My girlfriend has many guy friends?

[LOL]

I don't think she is taking your relationship seriously, she doesn't think you two are exclusive but she likes you so that is why she is still with you.
I think its fine for a girl to have guy friends when she has a boyfriend, but it is completely unacceptable that she hasn't told them about you, and acting the way that she does is wrong.

You should talk to her about this, and if she doesn't really care, then I don't think she likes you as much as you want her to and you should give your relationship a second thought. If I had a boyfriend, I would never ever do anything do hurt him, or do anything that would jeopardise our relationship in any level.