Spiteful baby daddy #1.

So I have a 5 year old son from a previous relationship. I'm now 6 months pregnant with baby #2 with my fiance who is not the father of my first child. My baby daddy and I have been broken up for a long time and he has wanted nothing to do with me until he found out I'm happy with someone else. Ever since ; he's been begging for me to get back with him promising me the world which I knew was a long shot because when we were in a relationship he was always talking to other women behind my back and was frankly a dead beat and did nothing. Didn't even work and didn't take care of the baby while I was working. Pretty much sat on his video game every day all day . Now fast forward over 3 years later he wants to try to re kindle stuff after realizing that I have finally moved on.I told him that I'm not risking anything with this new man in my life for someone that didn't even treat me well in the past. Fast forward a little bit my new boyfriend ends up proposing and we decide to get pregnant. The whole time my son's father still begging me to leave my now fiance for him. Promising things would not be how they were before and swore up and down he was not talking to nor interested in ANY other women and was determined to prove that to me. (he didn't know I was pregnant yet). Then a couple weeks later he finds out I'm pregnant . Instantly he starts calling me a whore for having 2 babies by 2 different men. And then proceeds to block me on everything (very mature right?) And tells me that if I have our son anywhere near my fiance that he will cause big issues for me. I've been with my fiance for quite a while now. A week after him finding out I'm pregnant ( a week after he swore he wasent interested or talking to any other girl and was begging for me back) I found out he already has a new girlfriend and is already bringing our son around her after threatening me saying I better not bring our son around my fiance. I don't know what to do at this point. I have no idea how my son is being treated when I'm not there. My son told me that if he says anything about me in front of his dad his dad gets very angry with him. I don't trust him at all nor the random girls he's having my son around and i just don't know what to do at this point.