<human>: Can you summarize the given text in a few sentences?

So a little bit of back story. My SO and I have known each other since we were young teenagers. We've always had a thing for each other but never dated; however, we have been very close friends ever since we met. A couple of years ago I was dating another guy and we had a little boy together. Bio dad didn't want anything to do with us, which was fine by me. I went off on my own and did really well being a single mother.

Throughout my pregnancy my SO was very supportive and the old flame we had started to rekindle. He would say things like I wish it was ours. Fast forward 5 months and we finally decided to slowly start dating. Everything was going really well, and he loved playing the dad role. I always insisted that he didn't need to do that unless he truly wanted to. Fast forward another 5 months he wanted us to move in together, but we both wanted to move out of state. So we ended up moving back to where he's from.

Things were still just as wonderful after we moved up until 4 months ago when he started his new job. He is always angry and moody now. He doesn't interact with my son at all unless he is yelling at him for my son just being a baby. My son is scared of him and my son cries if he tries to get close. My SO has left some bruises on my son when just doing basic things with him like teeth brushing, nail clipping, diaper changing, etc. I have had very serious talks with him about this and he apologizes but doesn't see the big deal of it. He's not hitting my son but grabs or holds my son so hard SO leaves the bruises. I no longer leave my son alone with SO and don't let my SO near my son without being present. I don't know what to do! Do I leave and not look back like I'm thinking about doing or do I stay and try to make things work?? Am I overreacting to this or am I right to not let him near my kid?? Please help reddit!!
<bot>: My SO wanted to be a father to my son who isn't his, but is now leaving minor bruises and yelling at my son. Do I leave or do I stay and try to make it work??