The same thing has recently happened to me, firstly I was a big AFC with a DJ front put on so I could charm girls but end up worrying about them "omg, she didn't talk to me today...".
However, recently I became so pissed off/dissapointed/upset at my girlfriend for a period of about a week ( because of her flirting with other guys, just like you ) I lost all loving feelings towards her, and you know what? I have never felt better. Maybe this is some stage of becoming a DJ, I am not sure. All I do no is now my life isn't ruled by girls anymore, so take this a step in the right direction.
As for what to do with your girlfriend, I'd give it a week or two before nexting her, it's quite common for people to go through stages of not loving their gf/wife whatever, so just give it time in case those feelings come back. And if they do, you should be more in control of your emotional ties with her than ever.
However if they don't come back, well you should be able to break up with her with no devestating effects on your side.
Oh and if you're wondering, I'm back with my girlfriend now feeling the effects described above, and its great to finally go through a school day hanging out with mates, having fun with the ladies and not worry about what my gf is doing, having faith in her.
Don't be insecure.
All my best and Good Luck