One major thing I see immediately is the mixing of pixel sizes. It almost always hurts the overall piece to be mixing pixel sizes.
Another is the gradient shading on the floor boards and walls. I think every pixel artist at your stage has done that exact same thing. I'd suggest looking at how games have handled interior wood textures.
Don't be discouraged, three months can feel long, but breakthroughs will come if you keep at it. Look for inspiration, look at others' creations in detail, continue creating, keep learning, and you'll improve.
