Hey mate I'm gonna tell you exactly what to do because I've been there probably even worse. I had oneitis so bad I was sick to my stomach literally throwing up I was so tore up over this girl, but what I want you to do is as soon as you get a chance delete her from fb delete her from your phone. I know you're gonna say you can't or you have this little sliver of hope you're clinging to that won't let you delete her fuck that just do it. I didn't think I could and I did it was a huge weight gone it was literally instant relief and closure you're just torturing yourself by seeing the fun stuff she is doing. Then I want you to watch the movie Yes Man with Jim Carey. That movie demonstrates the best way to get over oneitis. I'll give you a little motivation when I was tore up over this girl I had to get my bloodwork done for boxing it didn't come back clear there was a chance it could have been cancer thankfully it wasn't so I had that to deal with plus the oneitis. I got past it and brother I'm dating 5 different girls right now I'm living life is good! If I can get through that sure as fuck you can get past your situation.
www.wayoftheplayer.com lots of good reading material on there that will help you.
www.livestrong.com lots of good articles on there about recovering from a breakup and what not I spent hours reading on there it really helped me.
Anyway mate consider that my boot meeting your ass now get the fuck out of your rut and have some fun!!