I don't want to stop talking to my friends because it would hurt my girlfriend
Why would you not want to stop talking with your friends?
We've known each other since we were five years old, it's hard to give up our relationship
It is wrong to end friendship with old friends. Keep your friends around as long as you can.
Why do I need to keep them around?
You'd hurt them if you abandon them for your girlfriend. You should talk to your gf and make it clear that those are your old friends and you cannot just cut them off of your life no reason.