Friend advice....?

Ok, Ive been thinking bout whether I shud ask this or not but it has been bugging me for a while and I need to know how to deal with it. I'll start at the beginning...me and my best m8 both got bfs before xmas&it was really gr8 at the beginnin cos we all went to the park& town etc. 2gether and were all really close. For a while stuff was great but then we both decided to split up with our bfs cos it wasnt really wrking out. My friend kinda went off me for a bit cos we weren't hanging out so much together and then she started making a whole bunch of new best m8s, skipping from one to the next. There were sleepovers etc. and i felt seriously left out. Then i was on msn and my ex tells me he and my best m8 have gotten really close and want 2 go out. She hadnt even told me first...the nxt day at skl she explains& says she wont go out wiv him if it hurts me. I say ta and prepare to move on. Then i find out ova msn again tht they r going out. I feel so rejected and depressed.What shud i do?