letting go sexually

I've been with the same guy for 10 years we just got married and we have a 2 year old. I've always been really shy when it comes to things like letting him know j want to have sex, taking charge and sadly even being on top(I'll do it but I hate the thought if him looking at my body). he's the only person I've ever been with and he was with people before me so I am nervous still that he'll have something to compare it to and the fact that I don't know what I'm doing when I'm on top and it hurts my legs 😥. I want to be able to let go but idk how. he has never complained about my body but I hate my body now and after having a baby and PPD I can't understand how he doesn't see what I see or that I need to get in shape.

please help me any tips will help.