I think my girlfriend likes another guy how do I know or what do I do?
Figure out if she actually likes him before you do anything. If she does like another guy, probably not the best girlfriend around.
when you see and your with your girl, try walking towards him and pass and see if she stares at him.
ask her.. talk to him..
Just ask her. She probably wont be offended, especially if you ask it jokingly.
Get used to the idea that relationships are fleeting and don't last.
Talk to her first then if she does go stop cheating on me