What would you do?

I just found out a couple days ago that 2 years ago my husband was talking to another woman. He said it was only about 3 months, started a little before our first son was born and ended when he was about a month old. He says he met up with her one time, told me it was when he walked to the corner market that he met up with her there because she didn’t believe it was him talking to her and that he kissed her. He said he came home and decided he was making a mistake and stopped all contact and told her and her friend to stop messaging him. I just have no idea what to do. I can’t stop thinking about it. I’ve told him since we first got together that cheating is my one deal breaker. He thinks that because nothing sexual happened that he wasn’t cheating, even tho I’ve told him I view even talking to another woman as clearly more than friends is cheating to me. Idk if I should just get over it because it was 2 years ago and focus on how good we’ve been doing or leave. When that happened and for months before he had been telling me he didn’t know if he could be monogamous forever and all this stuff, but it all ended that year and especially this year he’s made it clear he only wants me and isn’t interested in anyone else either sexually or emotionally. I just feel betrayed and lost. I know it was just a kiss, but still. It was someone we’ve known for a long time and she’s always been obsessed with him, which he says that’s why he talked to her because he felt undesired by me and she always obsessed over him no matter what. What would you all do? Help 😭😭

Edit: I found out because during an argument he was trying to accuse me of cheating for the fact that his old best friend, who I dated after high school, messaged me once and asked for me to tell him to contact him because he wanted their friendship back. I told him he wasn’t interested and left it at that, no other messages. He still won’t get over this because I didn’t tell him right away, which I already apologized for. He brought up his past mistakes too which I knew of all but this one. He says he never told me because he thought I knew supposedly and that we weren’t bringing it up so we could get over it. Dumb excuse 🙄 I didn’t even know he was talking to her that long, although I did know he was talking to her a little, but I forgave that because I believed he never met up with her and realized his mistake. Now two years later I find out they did meet up and this kiss happened. He said he was only sitting in her car for 20 minutes and came home, and even described the exact time it happened because he had told me he was going to the store for a drink and I had asked him what took so long (it’s a 15 minutes round trip, which was doubled) and he told me he ran into his brother who lives down the street. So I know it wasn’t long.