What do you do?

Corinne
What do you do when your best friends replace you with someone new? My best friend (who I've known since I was three and current roommate) and another girl who will also be my roommate next year, have start to act as if they've completely dropped me from their lives for another girl. They speak to me civilly but don't want to hang out any more. The three of them are always going out and not inviting me. My roommate now is never in the dorm anymore. When I try to talk to her about it she kind of brushes it off.
I don't know what to do cause it hurting me so bad that I'm constantly upset about it all. I don't know if I'm just being dramatic or what. Please give me advice...