How to let go?

How to let that pain, hurt, & anger go😭? How can I let my guard down, & let the man I be with almost 4 years love me? When I was in love with him he was doing his selfish things(cheating). Which strayed me away now he wants to love me. I can’t just allow him in. I feel as though he’s going to hurt me. We share a 3 month old, & I want to work it out for her sake if possible. I had been a single parent for many years so I know how it feels. I’m capable of doing it alone, but I rather not. I’m not sure how to allow him back in. He’s been showing that he wants me, & only me. However there are times that he will bring up something random which triggers an argument. I feel like if we moved past something then why are we touching basis back on it??? Hopefully I’m making sense I’m just NOT sure anymore...