My girlfriend and problems that i have created and am asking for help?

Ok i go to college and my girlfriend is still in high school, but we have been dating going on 2 years. I made a new friend at college who was female but didnt tell her that i had a girlfriend and i didnt tell my gf that i made a new friend. And also my gf didnt want me to have a facebook cuz her uncle talked to some girl on facebook and cheated on her aunt with that woman. Well i made a facebook and didnt tell my gf about it. Well she found out about my facebook and then she found out about this other girl and they even talked and before they did she asked if i had anything to tell her and i said no and then after talking to that other girl she found out a bunch of things like i made the other girl a card, asked her if she wanted to ride with me to the library, have lunch and meet up with me thats it. Nothing physical. So after all that happened i had to give my gf access to my facebook and myspace and she went through everything and my hotmail. Well she said i couldnt have any more girls that were friends cuz i hid this one girl and who would say that i wouldnt do it again. And i wasnt allowed to talk to anyother girls either. So after that a couple of weeks later an old friend of mine who was leaving to go out west, i met up with and she and i just hanged out and talked and thats it. Well my gf surprised me and asked to see my phone and she also deleted all the girls numbers in my phone and she found that i talked to this old friend and she asked what it was about and i said that she called and i told her off. Well she got my old friends number somehow and she asked me before she called her if there was anything i wanted to tell her and so i told her everything and she thought that i was at my grandmas when i went and hanged out with this old friend. So her family knows and is super pissed at me but she doesnt know if she wants to break it off and im trying to convince her that ive changed and i have cuz i have learned a hard lesson that wont have to be repeated. So how can i get her to give me another chance and also how can i do the same with her family?