How to deal with mean, controlling, girlfriend?

Hello,

I need some advice on how to handle my girlfriend. We've been together off and on for about 5 years now. But over the 5 years I've watched her slowly change into the person she is today.

We argue over the dumbest things daily. She constantly brings me down, upsetting me or making me angry. I haven't seen her crack a smile in weeks. And lately she's been doing everything she knows upsets me.

Just recently she started telling me things that I say are stupid. For example I said maybe she should find a new hobby, and in response she told me that was one of the stupid things I say.

There's a lot more but I don't feel like making you guys/girls listen to all my problems =P.

Any advice? Thanks.
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Oh, and I tried talking to her about it but every time I do, she just ignores and starts telling me the things I do wrong or whatever she doesn't like about me.
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Thanks everyone for the answers, I can't pick which is best!
How to deal with mean, controlling, girlfriend?
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