Help ?

My boyfriend and I have been together for a year and a half. I love him to pieces, prior to that we've been on and off for 3 years so we've basically been together for 4 and a half years. He's my first love, you know. All that lovey dovey type thing lol. I've stuck by his side through the best and the worse. I've stayed with him when we he was sleeping on the floor, I'd even sleep on the floor with him cause I didn't want his body aching. Whenever he's sick I would come from working 12/13 hours shifts and catch the bus 2 almost 3 hours away to his house and I'd bring him anything to make him feel better. If I had $5 and he needed it I would go days starving just to make sure he was eating. Literally. So, he recently got a job (of course I'm more than happy for Him, but ever since then he's become a complete ass. We argue a hell whole of a lot more, he constantly accuses me of cheating (despite the fact Ive been faithful to him since day one) and everyday we get into some sort of disagreement. When it's good, it's great last for a few hours or so but when it's bad it's terrible. I've never ever thrown anything back in his face, I always made sure he was okay (and still do) when nobody had his back. I'm pregnant and he stresses me out so much with the fights and arguments I haven't gotten the chance to tell him our baby is in distress and I've been bleeding lately because I'm scared he'll blame it all on me and start another fight with me that'll last days. I need some advice.