I have a guy that is like one of my best friends but he has a girlfriend! Help me!?

Okay...this guy is like seriously one of my best friend! he would do anything for me and I would do anything for him...but he has a girlfriend and i mean I don't care cause i don't like him like that but I don't think she likes me so when she's around him it makes it really awkward for me to talk to him...which is all the time! So do I still talk to him anyway or just ignore him when his girlfriend is around so she doesn't get all pissy? or do I just talk to him about it? I'm so confused!