Help please

I'm currently 30 weeks pregnant and the father of my child (my boyfriend) decided about 2 weeks ago that he doesn't fully believe the child is his because "I'm a cheater and a liar" (I cheated on my last boyfriend with him, long story short ex threatened to kill himself when I tried to break up with him and I didn't know what to do). He's very paranoid and jealous too. He's constantly taking my phone and going through my messages and phone history and questioning who I'm talking to and why. I haven't left my house to hangout with anyone in over 8 months and never talk to anyone who isn't family anymore. Honestly I'm feeling trapped. He has a 3 year old son who we have 50/50 and 90% of the time I'm left watching him and taking care of him, even on the weekends and when my boyfriend is home and I'm getting so tired of it and fed up. I feel like I've been just thrust into full motherhood while trying to deal with my first pregnancy and soon to be first child. Boyfriend has also on many many occasions kept me up all night to yell at me because he's angry or frustrated (he has a bad habit of taking his anger out on me). He has shown some physical things, like grabbing me so I can't leave or dragging me or pushing me down to the bed. I've also been insulted by him many times (I'm stupid and selfish apparently) and insults my family (who are kind enough to let him live in the house with us). He keeps threatening to leave me too. All the time. But after every fight he comes back telling me he's sorry and hugging me and all that. Pretty much I'm getting fed up and am lost on what to do. I do love him but I'm afraid this will get worse after the baby is here.