"My biggest regret was not being with you when I had the chance".
Sorry, but no. I think that is just sad and pathetic, to be honest.
If you wanted to be with me, you should have taken the chance when it was offered. Plus, he is basically telling me that he wasn't 100% in his last relationship, which lasted almost 9 years. That is supposed to make him more attractive? That is a ridiculously long time to be with someone when your heart is elsewhere. Am I supposed to jump at the chance to be with someone who was mentally cheating on his girlfriend? He chose her over me. Plain and simple. So now that he is willing to give "us" a shot, I should fall into his arms and let him sweep me off my feet?