Not necessarily lessons, just going in and drawing a real person for a few hours. I do classes at university but there's also a couple of student run sessions where everyone just chips in to pay the model, and is open to the public, I'm sure you could find something similar.
The gap between drawing a real 3d object and something that's already been translated into 2d is immense. Plus if you find the right place everyone there is learning as well so you can still get the feedback in a more immediate way. And you'll also see a variety of different body types and real people posing in a way that is actually natural. Posemanics and photo reference are great but they've got nothing on reality when you're talking really learning the human form.
Your drawings here tell me you don't really need to READ about anatomy, you just need to practice, and in my opinion that's the best way to do it. I found
this quite useful when I first started but I never got past the skeleton stage. I think it's quite affordable compared to other resources as well.
