Past resentment causes me to get the nagging thought that I can find someone better than my current boyfriend?

My current boyfriend and I are both in our early 30s and have been in a relationship for almost 2 years now. Nowadays, he treats me extremely well and does everything a woman would wish for in a partner. He buys me flowers, he takes me out on dates, he's very verbally and physically affectionate, he's supportive and attentive, he's consistent, and he's communicative throughout the day and sends me long loving messages. However, the issue is that during the first year of our relationship, he did and said things that I can't seem to forgive or forget and even with how amazing he has been behaving now, it doesn't erase the resentment I already have towards him for his past mistakes and I'm not sure what to do. During the first year of our relationship, I caught him still checking his dating app (the one we met on) here and there... while he didn't talk to anyone on there, I still consider this straying or an attempt. He has also compared me to his ex and has used her to insult me. His ex was a teacher and I work in real estate and he told me she was a good person because she taught kids while realtors are scammers and only care about money. He told me his ex was tighter than me.
He told me loved physical qualities of his ex I clearly don't have (he said he loved her wavy hair and I have pin straight hair). He admitted he said all of these things during arguments to intentionally hurt me. Fast forward a year, I still can't move on from any of it. He has completely stopped all hurtful behaviors and is amazing towards me now but I'm afraid it's just a little too late. I sometimes wake up in the morning realizing I had dreamed about being in happy relationships with other men. I often wonder if there's someone else out there that could treat me better even though my boyfriend treats me well now. Do I have commitment issues? What is wrong with me? Should I forgive him for his past
mistakes or were those his true colors?
Past resentment causes me to get the nagging thought that I can find someone better than my current boyfriend?
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