Ive never felt so depressed in my life?

my girlfriend and me are going through some really hard times. were both college right now and have been together for 3 years. she always said she was really in love with me and i believed her. i trusted her more than anyone else in the world. but this year we have been fighting a lot and we always have small meaningless breakups and always are fine. she has always been really sensitive and told me all her feelings and and wrote me letters. i have never been like that but i loved her a lot. the main thing that happend is one weekend we left a bar and got in a fight and i pushed her away from me and she fell in front of some people. since then things have been really bad and weve both said a lot of mean things to eachother and then she did her own thing for a while like going out with her friends and drinking. knowing she was out doing that really made me sick inside becuase anything could happen to her and shes not a good drinker at all and makes bad decisions. i tried really hard to get her back and basically begged and told her how i would be so much nicer to her and take her out all the time and not her names anymore which is something we both did a lot but i really dont want to anymore. after a lot of begging i finally got her to come over a few times and talk. she even spent the night with me the last two nights and everything seemed great. she wanted me to cuddle with her and kiss her and stuff. but when we are apart she totally just turns on me. shes been talking about how she wanted to go to a comedy show tonight becuase this guy in one of her cles is funny and she wanted to see himn perform and he asked her to go. i really didnt want her to becuase i wanted her to stay with me especially because she didnt want me to go with her to it but she wanted to go with her friends. i asked her a lot to not go and i would take her to a different one tonight and last night she told me she wouldnt go becuase it would hurt me but today she totaly changed again and i couldnt stop her. she promised me she wouldnt drink but ive been texting her a lot tonight and shes responded to me twice and told me she was drinking and didnt say anything else. i have no idea what shes doing and she said she would leave after he performed but shes been gone for hours. she keeps lying to me about everything and ive felt so betrayed because everything ive said to her has had no effect. she doesnt care what i feel anymore and theres nothing i can do. i love her so im afraid ill keep taking her back and shel keep doing whatever she wants. i feel like she doesnt care anymore because she always complained about never having any friends but now she all of sudden became friends with the biggest skanks at this school, and she doesnt see how shes changing or doing anything wrong. i think this is the kind of life she wants but she keeps saying she loves me and knows shed want to be with me but im afraid she really has fell out of love with me, becuase she is hurting me so bad and doesnt care. my biggest concern is about the girls she decided to ociate with becuase i dont want her to turn out like them or ppl to think shes like them. shes started talking to guys on fb and has guys numbers now. its so hard becuase she leads me on and i feel like everything is normal and then she does this and says she cant explain what she feels about me and that shes just really mad at me but it gets me cuz she doesnt act like that when we are together. i dont think i can stand going to the same school as her if we arent together and seeing her out with them, but i feel like i cant trust her anymore. ive had such a sick feeling in my stomach and have eaten like once a day if that for like a week. i jsut want her back and not have any one else in our lives. i dont know if i should tell her if we get back together that i dont wnat her talking to those girls anymore because they seem to be fueling all the problems. im so lost and dont have anyone to talk to. ive gone out with her before when we were together but i knew i was more responsible but i knwo i wouldnt do that anymroe becuase this hurts too bad. what the hell should i do? anything i say isnt getting through to her but i think she knows i love her too much to really leave her