Start drawing from life, bro, if you do for a few hours every day I can guarantee you will improve. Doesn't matter what your subject is as long as you're taking the time to learn to observe and study it.
Supplement this with anatomy studies. Bridgman, Loomis, Vilppu, there are plenty of resources for you on the internet. You gotta get a strong understanding of anatomy and proportion before you can really do fetish stuff.