DO NOT e-mail her boyfriend. You will only be creating drama and you won’t solve anything. Your issues are not with him. Your issues are with her.
She had [i]ex-sex[/i] with you. It doesn’t necessarily mean you’re getting back together. It may have been just sentimental. There’s no reason for you to break up the relationship she has with her boyfriend. If you decide that you want to continue to see her, then you can pursue that relationship knowing she has a boyfriend. You can try and win her over — but if you do, do it with some integrity, not by “being mean.”
That said, my advice is to think it over. Consider the reasons you broke up before you decide to pursue her. You may have just been feeling sentimental, too, and by next week you’ll find that the romantic reunion you had with her was a fleeting moment and not a meaningful catalyst to get back together again.
Regardless of what you do, it’s up to HER to tell him about her liason with you. Not you.
I hope that helps. Let me know how things go, and please follow me @AskAprilcom on Twitter and on Facebook at this link: [url][/url]. 😀