I think feeling forced into it can gender your mood for sex. If you feel like it is a chore, then it is not very exciting. I think sex is best when it happens naturally with affection. Feeling pressured to please someone leaves your needs unmet. I can see the turn off there. He may just be considering his desires without considering your wants/needs.

I think doctors can give you a hormone test. It could be your estrogen is low, and that creates some of your issues, along with others. Taking care of a 1 year old and having a child is also major life events that can chnage your priorities.