I think my marriage is in danger.

Hubby and I have been together for almost 15 years now, but about 3 years ago, he confessed that he hadn't been sexually attracted to me since I was pregnant with our son (who was 10 at the time). I was devastated, but stuck it out because I thought maybe things could get better. We'd been having plenty of sex before hand, and I couldn't tell there was anything wrong. Then about 2 months later, I got pregnant with our daughter. He hadn't said anything about my weight or anything and we still continued having sex like nothing had happened. After she was born, I asked him again, because maybe things had changed. They hadn't. He still claimed that he wasn't sexually attracted to me. He said he still loved me, and otherwise he's been a good husband and a great father but he's just not attracted to me, even though we still had sex. And now I'm pregnant again, but this time we haven't had sex in the last 2 months. Either he's too tired and angry from work, or the baby just isn't cooperating. Plus he just seems so harsh and angry and frustrated all the time. We're arguing more than usual, and I don't know if it's because of outside stress, because of the pregnancy or because of our lack of a sexual relationship. I don't know what to do, and I feel like shit most of the time, but I love this man and I want to make it work. Any advice?