How do I get my girlfriend back? She's being cold and bitchy

So basically we just broke up about a week ago. The main root of the problem is I didn't feel comfortable with her hanging out with guys or constantly text messaging them. She understood and respected that. Recently we got in a fight because I just came back from vacation and wanted to spend time with her. I was with her for the day, then randomly out of no were she said she wanted to go hang out with her girlfriend in a few minutes. So I got upset, and said "So your going to give me a time limit as to when I need to leave you?" and she showed no remorse and I got aggravated and said were done because I was getting upset she stopped caring about my feelings. She said "I'm sorry to hear that." and left. I got upset that she didn't even try to fight for us, and that it's always me fighting. On new years I messaged her and said I wanted to talk and she said "I got nothing to say, things just don't feel the same any more." and was being very short and cold.

In the beginning of our relationship, I played very hard to get, mysterious and hot and cold. But after a few months, I fell for this girl (which iv never done before), and opened up to her completely. I made sure she always had a ride home after school, made sure she was always feeling like a princess. I had many incidents of her flirting with guys, and CONSTANTLY messaging her "guy friends" and posting comments on their facebook pictures saying "aww your so cute <3" but she would NEVER show me that attention.

Recently I started seeing other girls, and one really likes me, and has been posting all this flirty stuff on my facebook. She got upset and told her mom "See what I dated!?". Now bear in mind, her parents love me. Even gave me a job after all this. I texted her and apologized, but then thought to my self, she hooked up with a guy the day after, and has a guy posting on her facebook flirting with her to no end (the same guy who almost cost us our relationship, but back then she fought for us and cried and showed me she cared, so I stayed.) So I texted her back, that "I had no reason to be sorry, have a nice day."

Understand, I really want her back. I love this girl. I miss how things were the first 4-5 months. I can guarantee I would start acting the way I did in the beginning of the relationship if I got her back. But she doesn't even give me a second to speak, and its killing me seeing her with other guys.

What do I do? Can I still get her back? I miss her like crazy, and feel very vulnerable. I'm like panicking... (sad to say. never seen my self like this.)

How do I get my girlfriend back? She's being cold and bitchy
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