Boyfriend won't have sex wth me

This is pretty personal and I can't believe I'm posting this here but I don't know anyone here so it's fine :) My boyfriend refuses to to have sex with me. I'm really upset about it because of the stress I'm handling with work, home and pregnancy. I would really like the attention and connection and I feel like it will help a lot but I just can't seem to turn him on. My first thought was that he may not be attracted to me anymore with all the weight I've gained from pregnancy. My second is that he may be getting "it" from somewhere else. He says he's just not in the mood and that has been his excuse for the past 2 months. I just feel really crappy about it and don't know what to do.