My boyfriend messed up big time and I don't know if I should forgive him or not?

Anonymous
My boyfriend kissed a girl 2 months ago and just told me about it. I broke up with him and he's doing everything to get me back. He had a panic attack when I broke up with him and he cried the entire day. He also reread my notes and told me what he would miss the most about our relationship. He knows that what he did was wrong and he wants to change but I don't know if I can trust him. Is he sincere or not? And did I do the right thing?
My boyfriend messed up big time and I don't know if I should forgive him or not?
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