Please tell me what to do its so serious !!?

hi everyone i have been in a relationship with my gf for more than a year now..3months ago we had a really bad fight and argument and after that she went out with a guy !! and she texted me on my cell phone saying that she is on a date with some guy and she is sorry i was a heart broken but i forgave her because she said that nothing went on no ual things between them just talking for 3 hours plus she cheated with him on line for like 3 hours befor she go and meet up with him!!! she strat saying i swear to god and crying and all that and i forgave her after that but i was really hurt and i believed her..today in the car i had ad argument and she told me the Truth that that night she made up with him and gave him a head that day...she was crying like crazy and all that and i love her so much but i'v never had a gf who cheated on me befor ..... i love thins girl and she feels really sorry and just want to get me back and any possible way ..but im really hurt i feel like my heart is bleeding ..what should i do should i end everythink with her or give her another chance ????