Should i move on?

well .. my bestfriend carmen liked my crush and he likes her too and then we were in an open relationship .. though she was my bestfriend and then .. i cried for him (nathan) five times and then when they stopped liking each other it was back to normal .. and after a while ago my BEST friend abegail , likes nathan and it was the same situation and when carmen liked nathan , abegail told me to stay strong and fight for him, but then now she is eatting her wrods and then .. i cried 1 time for him during the concert because nathan put his arm on abegail .. and i just dont know why she will betray me ..if she was my friend she would've not hurt me and wont go for him right ? .. i dont know what should i do ? i liked him since school started and i just cant move on .. and i talked with her and then we cried though she was still like " i still want to give nathan a chance " ... what should i do >:( move on but how ?