Theres something about using a thicker pencil/brush that makes the work look more professional and easier (at least for me), try using a thinner pencil (at least when cleaning up a little) so that it looks more detailed. When you replace the thick lines with thin, you might see more which places lack squish/strething, folds, subcutaneous muscle/bone details, etc. When we use thick lines a lot of smaller details like wrinkers and folds can be ignored becuase of the thick lines. I'm studying anatomy from Proko videos now, that should help alot on actually realistic body pieces coming together (like your leg in the third image has nice opposite curves gesture but obviously not very realistic)
