How can you tell if this guy has a girlfriend and likes you?

I just have this huge crush on this guy and I would like to know if he has a gf but it looks to me like he does but i'm not sure. Because everytime i like a guy it turns out that they have a girlfriend. But everytime i see him he gives me a head nod hi dunno how u say that and if he sees me again he waves a peace sign when he was leaving. I just really like him he's the first guy i liked since wat happened with another guy. But I'm so sad cuz i like him i wish we were together and i'm not sure if it's gonna go newhere since my luv relationships has gone down the drain and i just feel like to give up. I've liked so many guys I fell in luv twice. i'm just heartbroken cuz i've never sorta really had a boyfriend and i just wish i had found my tru luv my soulmate.