I am not any expert but I would HIGHLY reccomend you to do a bit of research about the muscles with the parts of the body you're having problem with; I was having the same kind of issue when drawing the basic forms of the face, but know that I can slighty comprehend how does the muscles display under the face is easier to draw any forms or curves of the face. Try to not get over everything at once, but to scan trough a group of muscles of your interest and observe them as layers or flat but stretchy tubes that "wrap" around the bone. That's what works for me, I dunno, I'm still trying to figure out anatomy as well.
