Bf trouble, need advice!!!

Ok so me and my boyfriend were together for 3 yrs and 6 months. I was going through some stuff on my own so I broke up with him. 6 months later we both felt like we could try again. He is the type of person that is very social and he is nice and funny and always happy!

I was looking through his phone just out of curiosity and I found messages of when he was single. I was shocked because he didn’t seem like that type of guy to be so bold so quick. But I blew it off saying to myself, well he was single. Then, I found messages of him texting other girls while we were together!! I ask him about it and he says “that’s when we were fighting and i was gonna break up with you”. These messages were a week a part. During this time of him texting other girls, while we’re still together, I’m happy with him and he seems to be happy with me. We were done fighting and had talked through it. He tells me during that time he was “thinking” about breaking up with me. He tells me now, he wants nothing to do with the other girls and that he doesn’t talk to them anymore.

I’m embarrassed and I don’t know if I should trust him. Please help!!!