Move on dawg, she dumped you for him, she'll dump him for "them". I've said it before, I'll say it again. Why would you want someone who doesn't want you? It hurts, get over it and move on. Guy's are guy's, when it comes to pussy, we know no boundries.
i know exactly what you mean. i just had a friend of mine whose girlfriend and him broke up like 2 months ago. they had been really serious about one another, and they were living together for like 2 years. he just found out yesterday that she apparently is 1 month pregnant now with his best friend's baby. how shitty is that? the only thing to do in this situation is to move on and find someone who will treat you like you should be and deserves to be with you. neither this girl nor your friend deserve to be with you if they're that calibur of people.