I really like this girl and she wants to be exclusive with me but I'm still banging other girls
Does she know that you're still banging other women?
No I haven't told her I've been with other girls.
If you really like this girl then you should do what it takes to make her happy.  That probably includes being exclusive, as most people prefer that you don't date several people at once if you're in a relationship with them.
What's the problem? Can't we all just be friends? Why would she care that all these other girls want sex?
It's possible that she would be okay with it, but people generally don't like when their partner is sleeping with lots of other people. If you want to be in a relationship with her you should stop sleeping with other people and be exclusive with her.