Just found out ex cheated while pregnant

Hi guys so it’s an odd scenario but I need to vent. I’m actually devastated. So while I was pregnant with our second child my ex and I were not loving together (it’s always been on again off again). When I found out I was pregnant he wanted to move back in but he was drinking and being reckless aggressive etc and I told him to please get his shot together during the pregnancy and move in when that happened. He then gets a young female roommate. This totally flips me out and fills me with jealousy and rage. He swears nothing will happen etc. one day I go over to pick up my older son and she’s in the kitchen she turns to me thinking I’m him with the sweetest smile…. I flip out and start yelling at her and he comes in with my older boy who’s 3 at the time and starts pushing me out of the apartment and screaming cursing in my face. (I’m about 4 months pregnant). I leave devastated and basically I find out today (4 years later) that he fucked her that night because she was “comforting him because I was so crazy). We recently were thinking about getting back together again because he’s finally sober and you know how the holidays are…. He accidentally confessed to this which he lied about for 4 years. He had moved back in when I was about to give birth. He was an asshole and a drunk again so I kicked him out when baby number 2 was about 2 years old. I feel so freaking violated and betrayed. I know it was a long time ago but it feels like yesterday. I hate that I’ve waisted so much time on this man and that there’s still a part of me who wishes we could be together when I know he’s a toxic dick face.