Need advice❤️

So a quick backstory:

I’ve been dating my baby daddy for almost 2 years but we’ve been each others crushes since high school. We finally got to talking 2 years ago and I knew he was the one! He was living out of town so we’d visit each other but he moved towns solely to be with me. It wasn’t long before I became pregnant so now i have a beautiful 8 month baby girl ❤️ we’ve both been drama free and he’s always treated me right. Well today he told me he cheated on me 6 months ago with someone he doesn’t even know. All he did was ask for a BJ but backed out because he was scared to go through with it so he touched her boobs. Please do not question the story because I do believe him, I just don’t know where to go from here. I went through really bad postpartum depression so while I was going through a crazy mental recovery, he did this. I really don’t know what to do. We have a baby daughter so I just want to do what’s best. Thank you for hearing me out❤️