i think you should try to see whats going on like talk to her more and pay attention to her and basiclly listen to her more and try to find out if she is or not because just that she believed you of all those rumors doesnt mean that ohh shes doing something its just probably that she realizes that rumors can get out of hand and people make lies to make there lives seem like they have one which they dont and she probably is just a big flirt and also she was probably doing that because you were emotional abusing her and she needs to feel sexy and pretty and beautiful not put down or anything so try to regain that trust try so much that the only guy she will be thinking about is you and no one else and that emotional abusing can really drive you away from somebody. but if she is cheating on you then dont try to help because you cant help someone that doesnt want to help themselves or even take your advice make her feel special because if she is looking for attention let the attention come from you not from random guys and you shouldnt snoop through her phone because if she finds out she will be SUPER pissed and then you might get another black eye but still talk to you and tell her you love her aND that your sorry and hopefully she sayd it back for making you all worried just make her fell like she has someone to come and talk to not like she has to hide something especially not from you (her boyfriend) . but TRY atleast  and if you try and fail atleast you tried you gave i a shot. and then if you try and succeed then awesome !!! =D