Sex problems someone help please!!!

I'm 24 and have been with my boyfriend for ten years we have a 4 year old son together & are trying for baby number 2! But the only problem is I just don't care for sex anymore (I know crazy right?!!) I feel bad because he's always telling me how beautiful and attractive I am and is ALWAYS in the mood and tries to get me in the mood but when he does try I get annoyed and then have that feeling like I'm doing something wrong which I don't understand myself, ( TMI alert!)  my ultimate turn on is when my nipples are played with & of course he knows that but here lately it just doesn't do anything for me! Usually it works even if I'm not in the mood that's the instant turn on but I just can't seem to get in the mood AT ALL. We have sex once in awhile & when I say that I mean MAYBE twice a month!! I need help!!!!! I use to love sex and want it like a normal person could it be that I'm just burnt out on sex?? I don't even really get wet please someone help me out what should I do??