Loss of words

so I don't know how to feel.. I've been with this guy for a month.. well about a week ago we were talking and he said how he feels like a total piece of shit. I asked why? well he told me he realized he still had feelings for his ex (He reached out to her without telling me). he apologized for hurting me and that he knew he was going to regret every ending our relationship.. I woke up the next morning and got a text from him saying he missed me and that he thought he missed her but they were false feelings.... do I believe him or walk away? We have great chemistry and clicked from the beginning.