Depression. Get out of this situation.

I have been betrayed by my gf. I feel a thrust upon my preatige and pride. I even feel betrayed, hopeless, loser. This cheating has shattered me.I want to take revenge by informing her parents about her current relationship. Once i was a very caring person, but after this incident i dont have any kind of feelings.I dont feel anything for anyone.I feel lost.Its been 4 months and still she haunts me in my sleep because of which i am not able to sleep properly. My mood is always sad.I travelled to places to keep myself happy, but this only happens till the time I am travelling after that i always get her thoughts.I know what is right and what is wrong but am not able to control myself, my emotions and my feelings. While doing any task I get her instance and tear roll down.help me i want to get out of this situation.