I agree that it could be your hormones. There are days when I feel like I should just pack up and leave, and there are days when I feel like I'm so happy with the way things are. If you're concerned, talk to your partner and maybe see a family counsellor. My partner and I are seeing one and I've really noticed an improvement in our relationship...even just in the way my partner expresses affection and is more actively involved in the pregnancy. I know that some of my problem at least was my hormones, and I'm glad I stuck it out and we worked on our relationship. At least I think you ought to give it a try.
You don't break up a home because you "fall out of love" with your partner. Is he abusive? Is he a bad father? If not, try to keep it steady. Express yourself in a constructive way. Relationships are not going to be fireworks all the time, they have ups and downs. The problem is nowadays people are ready to throw in the towel so quickly, only to move on to a new relationship which eventually has its own set of problems. All the while the children don't get the benefit of growing up in a steady home environment because their parents "fell out of love".
Its probably just your hormones honey. Have you felt this way before being pregnant? Try talking to him about what different and whats not the same. Hope this helps.