I guess I understand why you feel betrayed. Like I was going out with this girl earlier in 2005 and she dumped me and then like a month afterwards I saw her with this other guy, and I pretty jealous and even like I was betrayed or something. But now that I think about it, she can do whatever she wants and it's not really my business anymore, so even if I feel jealous or betrayed I guess it's just self pity. Like when I see her now with some other guy I'd be thinking subconsciously "She should be mine! Arrgh!". I've pretty much got over her now though, it just takes a little time.