I don’t know what to think or do 😣

Last night my boyfriend was scrolling through his texts and I saw one from his ex. So I grabbed the phone and opened the conversation. The texts were dated a few weeks after we had officially started dating. The texts were him saying to her he wanted to be with her and all that kinda stuff. It really hurt me. Even though we were brand new/ 1st month of dating. It’s been a few months since that happened and things have been amazing. So I’m not sure if I’m over reacting or what. I don’t know if I should let it go or move on. I’m trying to move past it but one text is burned into my brain “I’m dating some girl that I wish was you and it fucking sucks”. That just killed me. I always feel second best in every situation so this is just hard for me. I’m really sad. even though it was when we were new I don’t know what I should do 😔