I found a girl I really want to sleep with, but I have a girlfriend
What else can you say about this girl?
A girl I know and like she is so pretty and I hear she likes me, so I thought why not give it a try
It is wrong to hook up with someone else while you are in a relationship. You should be honest or break up with your partner first.
I like to be with other people and I probably need a more open relationship with my girlfriend. It is a way better as it gives freedom to be with someone else.
I'm happy for you that you are figuring out your sexual preferences, but I don't think it's very fair for your girlfriend. She went into the relationship expecting only you, so how would she feel seeing you sleep with other girls? Why not peacefully discuss it with her, and if she doesn't agree, part ways amicably so you can find the open relationship you want?