My girlfriend kissed another guy (or he kissed her one or the other)?

Well this is how it happened... : So i got suspended from school for other reasons (total accident) but anyways so i come back from rhode island and I start txting up my friends my bestie says she has to tell me something but doesn't want me to get mad..Immediately I think it was about my gf idk why tho. so anyways my gf txts me out of them blue the nxt day when she get her fone/ipod back and says we gotta break up because her parents found out about us dating, she says she still loves me SO much and I mean the world to her. First i really don't see why we have to because we have been sneaking our relationship for a WHILE ( 3months) ... btu anyways she then tells me she has to work on things with her family..i respect that, so i say "ok lets just be friends"..but then my bestie later tells me that my gf goes up to her and says that she kissed another guy. O.o WTF? she did it behind my back...take note this aint the first time, i forgave her the first time i guess it was accident. So again out of RANDOM ( I guess it wuz because i was telling my bestie that i wanted all of my gifts that i brought her back) my gf decides to txt me. She txts me about how I want my stuff back or "OUR" stuff , and i give her a attitude i tell her she can keep the stuff idc. but then after my gf wants to know why i have a attitude and she continues to ask and pester me, i just tell her i don't wanna talk about it and that il talk to her later in school when i get back. right after my bestie texts me and says that my gf keeps txtn her and asking her if she told me what she did. I tell her to just calm down and pay my gf no mind. well after that gf thinks that im mad at her cause she choose to break up with me because of parents. NO thats FAR from the reason i was upset. It was more because of the fact that she DIDN'T tell me (and still hasn't), that i had to find out from some one else, and that she kissed another guy. Lastly i want to add that she txted my bestie saying that the guy kissed her and she doesn't really see the problem, that she only loves me. and finally she thought (before i cleared it up) that i didn't love her no more. PLEASE help idk wat to do im still mad but like its wierd idc at the same time