how to say sorry to your girlfriend... :'(

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thoughts came into my mind..i was afraid that one day she'd leave me or cheat on me..because when we're together, she frequently mentions about her crushes..her crush on our professor..her crush on a celebrity..(may about 1 out of 10 times)..she even calls this celebrity her boyfriend (in a joke manner)..but it really affects me..it made me feel i'm just one of her loves..and not the ONE..well that's how my instincts interpret it..but maybe there's a chance that i'm wrong..in the past, she also became jealous of one of our classmates..she didn't talk to me..but i made the move and talked to her..explained everything..she was convinced then..starting from then on..i didn't talk about this girl..up to now..and also about other "chicks"..just to prevent jealousy on her part..because i know and understand that feeling..so i made her feel she's just the ONE in my life..but later on..those things happened..i told her it makes me feel uncomfortable as she was in the case i mentioned..but she repeated it again..although unintentional because she said sorry immediately..but it really pierced through me..OUCH.. i didn't brought the matter up to her..i just changed my attitude a little(but i still talk to her smiling)..although deep inside i just want to drink and drink..then i really drank..together with my friends..two nights of drinking..and i didn't text her at all night during the second night.. so now she became mad at me..through text messages, i said i'm sorry..can we talk?..but she said we can't..she said she's too affected by what happened..i lowered every bit of my pride and said sorry to her..about 20 times i think..but still..she said we can talk about it when we meet.. today(2 days after her getting mad)..we will meet.. any suggestions on how i can do this?..say sorry to her sincerely that she will really feel that i'm sorry..and at the same time she would understand what i felt?.. thank you very much..