Should I keep my word on divorce

Hello everyone I need help
I just had a baby a month ago. I have a mixture of postpartum depression and postpartum Rage. This is my last baby and feel like my husband has helped me so much more than with my previous baby. I feel like this has been the best time our marriage has been through. Going back to my postpartum rage, I been mad at my husband for 2 days because of it. Last night he had a boys night out that he had already planed 2 weeks ago. So he got home and I decided to go through his phone (I know it’s pretty toxic of me but this has been the first time doing it in probably more than 3 years) and I found messages with someone he used to date back in highschool (she doesn’t live in the same state we do, and he has never been out of state without me). I saw pretty old messages of him calling her baby. But I also a found out that they had been messaging for the night he went out with his friends. The messages were nothing serious. I confronted and asked him what was going on. I promised me there was nothing going on and that he was drunk when he was messing. After he said that I told him that the best was to get a divorce. He begged me no to do it. At the moment I felt like it was the best thing to do. I asked him why he did something like that when I need him the most. He knew I was so vulnerable because of my postpartum. He told me so many times he was sorry that he never wanted to hurt me and that I deserve the best. After he saw I wasn’t changing my decision of a divorce he told me he was going to respect my decision but he wanted me to stay at our home just for me not to struggle with our kids finding a new place. I told him I didn’t want anything that we built together, I told him he could keep everything.
A whole day has passed by and I don’t know if I over reacted or if I should keep my decision. I really love him and a part of me feels like I didn’t have him a chance to explain himself. But my other part says to leave him and give me my place.

What should I do?