Well, you've come to the right place, because I'm the king of screwups, especially lately. So I know how you feel.
Yes, you messed up, but you already know that. I blame your boyfriend more for using you for easy sex, but it takes two to tango. Neither of you did the other any favors. You feel used and he's cheated on his girlfriend. Lose-lose.
Keep in mind, though, that a lot of people continue to have sex with an ex after they've broken up. You have a history with this guy, and feelings don't just go away overnight. It's very easy to remember good times and fall back into the emotions and habits that drew you two together in the first place. So, what you did was understandable. Wrong, but understandable, and another reason I'm a fan of clean breaks.
Regardless -- what's done is done. So you screwed up; congratulations, you're human. Not one of us is perfect, and never will be. Feeling regret is appropriate and helpful -- guilt's a great teacher -- but continuing to pummel yourself mentally isn't helpful at all. Wallowing in regret and self-loathing is counter-productive, and could actually land you back in his bed again if you're not careful.
Making mistakes doesn't mean you're a bad person or a loser. It means you're normal. You recognize that you screwed up, you regret it, and I'm sure you've vowed not to let it happen again. If you haven't, that's your next step: don't let it happen again. Stay the hell away from your ex, and ignore any communication from him. He has a girlfriend, and you don't need him in your life to be happy. Make the clean break now that you should've made long ago.
Beyond that, it's over. Let yourself off the hook, buck up and move on. Life's too short to wallow in shit.
Yes, excellent answer. Live and learn. Forgive yourself and move on. You can't undo what you've done. Just realize how and why it happened and try to do better the next time around.
Best answer ever [=
Lets not get started on the fact that your ex boyfriend cheated on his current girlfriend. I hope he wasn't up to the same business when you two were together!!! Yeah, I said it.
Once again, an awesome answer from The Mighty Wise-Ass!
Cary's right; we all do things we regret, but then we haul ourselves up, shake off the dust, and move on. I've messed up so many times and in so many ways that if I had a nickel for every time, I'd be rich.
Just chalk this one up to "a one-time thing" and forgive yourself already. :)
Good answer..I like the last statement!!!!