I am so sorry you're going through this. No-one at all deserves to be treated this way. You need to think about what's best for yourself, your son and unborn baby right now.
Your DP (or maybe XDP now) is still very young. Men take longer to mature than females, it's a known fact, and it sounds like he's still living like a teenager. You need to step up and be the adult here that your children need you to be.