Pregnant, angry, and my boyfriend can't handle it?

Hi, I am 29 weeks pregnant and feel like I am going to lose it. I have been on medication for depression for 3 years and have always been a bit of an irritable person I guess.It comes from having a cruel mother probably. Anyway my emotions pretty much from the beginning have been pretty out of whack, and now in my 3rd trimester I feel like I should be checked in to the loony bin. My fiancee, who has anger issues, is getting understandably fed up with my constant irritability; knowing this, and noticing the eye rolls, and frowning only causes me to feel irrationally angry. We then fight pretty bad, he yells and doesn't care if our roommate (who just moved in, and we just met) hears us, and he takes things I say the wrong way and now is going to leave because he thinks I said we need a break. I told him I would go stay with a friend for a week to give him a freaking break from me, not that we needed a break. I feel bad but don't feel in control at all and don't know what to do. I can't handle these emotions, and feel dumb blaming being pregnant, but what else could it be I am losing my mind, I get so irritated with him all the time. When he yells at me I want to go hide and get to the point where I scream and want to rip my hair out. I know he is going to come home tonight and be all crazy mad at me because he thinks i want a break, and we are going to fight again, and he will yell and my poor roommate will have to hear, which is embarrassing. I don't even want to be here if we are going to fight. And when he thinks i said something one way and that's what I meant, that's the end of it he doesn't believe me when i tell him otherwise and wont listen to me when I try to explain. Sorry this is a bit all over the place but I am so frustrated, and this can't be good for the health of the baby either. I am having a complicated pregnancy already and am on bedrest, which hasn't helped our already suffering finances to top it all off. I don't want to make him sound bad he is a very good guy, he is very sweet to me and does a lot for me. I just don't think he can deal with me anymore, i can barely deal with me. What the hell is wrong with me?