He texted his baby momma..am I over reacting?

So I'm dating someone. We've been seeing each other for over 6 months. We've been exclusive and now we're dating, been dating for a few months.

One weekend I noticed he was really upset when he had his son. I tried to ask what was wrong and I tried to comfort him, he's going through a TON of stress. Grandparent dying, custody court, and just money problems. We were upset with each other because i had been tired of the cold shoulder, he doesn't communicate well. After he dropped his son off he came back and got drunk, I took a nap. I woke up to his BM texting me, showing me that they were arguing. The way the he was arguing with her was very similar to texts they had when they were trying to fix things. Arguing in circles for no reason. He obviously wasn't going to tell me he texted her, so he was hiding it. I know that's how cheating starts, with sneaky conversations. He told her that he cries himself to sleep which I know he doesn't do when I'm here. He threw it in her face that she cheated, he said "just go to sleep in your little bed or do whatever it is that you do I'll just stay up and be depressed". They argued for maybe 30 min.

Both say they're done but It sounds like they're both not over it and just are arguing just to argue. Like he was trying to get a pitty fuck is what I think?. She says shit all the time to piss him off to make herself look better, so I guess he went off.

He told me he litterally stayed up all night. I texted him "why tf are you boo who texting her?" And he never answered me. He stayed in the living room.

I'm at a loss for what to do. I'm extremely hurt. What do you think? Am I over reacting? (They broke up cause she cheated) they're going to court for split custody.

For some reason the app won't let me post the text.