You've done the math. You’ve tracked the apps, bought the ovulation strips that look like middle-school science experiments, and honestly, you’re exhausted. It feels like everyone on Instagram is announcing a pregnancy with a "oops, it just happened" shrug, while you're sitting there staring at another single pink line. It’s frustrating. It’s isolating. And when you search why can't get pregnant, the results are usually a mix of terrifying medical jargon or patronizing advice to "just relax."
Relaxing isn't a medical strategy.
The reality is that human reproduction is surprisingly inefficient. Even in perfect conditions—two healthy people, perfect timing—there is only about a 20% to 25% chance of conceiving in any given month. Those aren't great odds. If a casino offered those chances, you’d probably walk away. But when it’s your life and your future family, you stay at the table. If you've been trying for a while and nothing is happening, it’s rarely just "bad luck." There is almost always a biological "why" behind the "why can't I."
The Timing Myth and the "Fertility Window"
Most people think they know when they ovulate. They don't. A study published in Human Reproduction found that only about 13% of women with regular cycles actually ovulate on Day 14. If you're banking on that mid-cycle date because an app told you to, you might be missing the window entirely.
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Sperm can live inside the female reproductive tract for up to five days. The egg? It’s only viable for about 12 to 24 hours. This creates a tiny, high-pressure window. If you wait until you see a positive LH surge on an ovulation predictor kit (OPK) to have sex, you might actually be too late. The surge happens before ovulation, but by the time the egg is released and the kit turns dark, the window is closing fast.
Think of it like catching a bus. You want to be standing at the stop before the bus arrives. You don't want to start running for the stop when you see the bus pulling away. This is why many reproductive endocrinologists—like those at the Cleveland Clinic—recommend having intercourse every other day starting shortly after your period ends. It ensures a "reservoir" of sperm is waiting for that egg the moment it appears.
It Is Not Just a "Woman’s Issue"
We need to stop acting like the uterus is the only player in this game. It’s a 50/50 split. Roughly one-third of infertility cases are linked to the female partner, one-third to the male partner, and the remaining third is a combination of both or "unexplained."
Male factor infertility is skyrocketing. Research published in Human Reproduction Update noted a significant decline in sperm counts globally over the last few decades. It’s not just about count, though. You have to look at morphology (shape) and motility (movement). If the sperm are swimming in circles or have structural defects, they aren't going to reach the egg.
Lifestyle factors play a massive role here. Heat is the enemy of sperm. Hot tubs, laptops on laps, and even tight underwear can raise the temperature of the scrotum enough to kill off production. It takes about 72 to 90 days for new sperm to be created. So, if a man had a high fever or spent a week in a sauna three months ago, his counts might be low today. It's a lagging indicator.
The Silent Culprits: PCOS and Endometriosis
If you’re wondering why can't get pregnant, and your periods are a nightmare, we need to talk about Endometriosis and Polycystic Ovary Syndrome (PCOS). These aren't just "bad periods." They are systemic issues.
PCOS is one of the leading causes of female infertility. It’s essentially a hormonal imbalance where the body produces slightly higher levels of androgens (male hormones). This prevents the follicles in the ovaries from releasing an egg. You might have "pearl-like" cysts on your ovaries, or you might just have irregular cycles and stubborn acne. If you aren't ovulating, you can't get pregnant. It’s that simple. But the good news is that PCOS is often manageable with diet, metformin, or ovulation-induction medications like Letrozole.
Endometriosis is different. It’s "the silent thief." Tissue similar to the uterine lining grows outside the uterus. It causes inflammation. It creates scar tissue (adhesions) that can literally glue your fallopian tubes shut or pull your ovaries out of place. Some women have Stage 4 endo and no pain, while others have Stage 1 and are in agony. You can't see it on a standard ultrasound most of the time. It usually requires a laparoscopy to diagnose. If your "why" is unexplained, endo is often the culprit hiding in the shadows.
The Age Factor (and the Anxiety it Causes)
Nobody likes talking about the "biological clock" because it feels like a looming threat. But biology doesn't care about our feelings. A woman is born with all the eggs she will ever have. By age 30, fertility starts a slow decline. At 35, that decline accelerates. By 40, the chance of conceiving naturally is roughly 5% per cycle.
It’s not just about the number of eggs; it’s about the quality. As eggs age, they are more likely to have chromosomal abnormalities. The body is smart; it often won't let an abnormal embryo implant, or it results in an early miscarriage. This is why many people in their late 30s find themselves asking why can't get pregnant even when they’re healthy and active. Their "ovarian reserve" might be lower than average for their age, something that can be checked with an AMH (Anti-Müllerian Hormone) blood test.
Blocked Tubes and Uterine Roadblocks
You can have the healthiest eggs and the strongest sperm, but if the "highway" is blocked, they’ll never meet. Pelvic Inflammatory Disease (PID), previous surgeries, or even an old chlamydia infection you didn't know you had can cause tubal blockages.
Hydrosalpinx is a specific condition where a fallopian tube is blocked and fills with fluid. This fluid is actually toxic to embryos. If you're doing IVF and have a hydrosalpinx, the success rate drops by nearly 50% because the fluid can leak back into the uterus and prevent implantation.
Then there are fibroids and polyps. These are non-cancerous growths in the uterus. If a polyp is sitting right where an embryo wants to land, it acts like a natural IUD. It’s a physical barrier. Removing a small polyp via a quick hysteroscopy can sometimes result in a pregnancy the very next month. It's often that mechanical.
The Role of Weight and Thyroid Function
Weight is a sensitive topic, but it matters for hormones. Both being underweight and overweight can shut down ovulation. Adipose tissue (fat) produces estrogen. If you have too much of it, your body gets confused and thinks it’s already pregnant or on birth control, so it stops releasing eggs. If you have too little, your body goes into "survival mode" and shuts down the reproductive system because it doesn't think it can support a pregnancy.
The thyroid is the master regulator of metabolism and hormones. Even a "subclinical" hypothyroid (where your TSH is technically in the normal range but higher than 2.5 mIU/L) can interfere with conception and increase miscarriage risk. Most GPs look for a TSH under 4.0 or 5.0, but fertility specialists want to see it much lower. It’s a nuance that gets missed constantly.
What to Do Next: A Roadmap
If you’ve been trying for 12 months (or 6 months if you’re over 35), it is time to stop guessing. Stop buying more supplements from influencers and start getting data.
Step 1: The Semen Analysis. It’s the cheapest, easiest, and least invasive test. Do it first. If the "swimmers" aren't up to par, all the tracking in the world won't help the female partner.
Step 2: Day 3 and Day 21 Bloodwork. Day 3 testing looks at FSH, LH, and Estradiol to see how hard your brain is working to kickstart your ovaries. Day 21 (or 7 days after suspected ovulation) checks Progesterone. If Progesterone is low, you might be ovulating, but your uterine lining isn't staying thick enough for an embryo to stick.
Step 3: The HSG (Hysterosalpingogram). This is the "dye test." They pump a contrast liquid through your tubes to see if they are open. It’s uncomfortable, but it’s the only way to know if the path is clear. Bonus: many women see a slight "fertility boost" in the three months following an HSG because the dye can clear out minor debris.
Step 4: Check Your Environment. Endocrine disruptors are real. Phthalates and BPA found in plastics and some "fragrance" in skincare can mimic hormones and mess with your endocrine system. You don't need to live in a cave, but switching to glass containers and "clean" detergents can lower the toxic load on your body.
Moving Forward
The journey of why can't get pregnant is rarely a straight line. It’s a series of eliminations. You rule out the tubes, you rule out the sperm, you rule out the thyroid. Eventually, you find the sticking point.
Don't let a doctor tell you to "just keep trying" if you feel something is wrong. You are the expert on your own body. If your cycles are 45 days long, that's not "normal." If you have debilitating cramps, that's not "just being a woman."
Start with a dedicated Reproductive Endocrinologist (RE) rather than a standard OB-GYN. OBs are experts at delivering babies; REs are experts at the science of making them. There is a huge difference in their approach to diagnostic testing. Get the data, build a plan, and take the next step based on facts, not hope alone.