<human>: So I recently started dating this guy. A few weeks in we had the exclusive talk and he wanted a relationship with me. Two weeks into this new relationship he tells me that his crazy ex is visiting town and wont stop bugging him to meet up. He tell's me that he told her he's moved on and seeing someone new. But that night I asked him if I could go to his place. He said no because it was too late and he was playing video games. At 4am he sent me a selfie of him sending me a kissy face. I could have sworn I could see a hickey on his neck. Anyways, I didn't want to be a nagging gf and harass him about it so I choose to trust him. 

Fast forward three weeks and I can't stop thinking about it. He's taken me to meet his family, we have travel plans already next month and have a lot of summer activities planned. Anyways, I finally get the courage to ask him about his ex and after him lying three times over a few days, he finally admits that he had slept with her. He also said that he regrets it, he was stupid and drunk and he was so mad at himself that he has erased her from his life since that night.

Obviously I was pissed. He got checked the next day and has done everything I've asked since. Half of me wants to think that this was a one time thing because his ex was the only girl he had been in love with, and that we were so new into a relationship he wasn't too serious yet. Should I forgive him or should I just move on? I really like him and I want to believe that it was a stupid mistake.... Am I crazy to think that?

Can you provide a brief rundown of the text in within 3 sentences?
<bot>: We just started dating and he admitted to sleeping with his ex while she was visiting. Do I forgive because we had just started dated?