Left in the dark

So I met this guy and we have been talkin for I say 3 months now,but ima kind of confused about what's really going on...when eva were 2getha and his phone rings he cancel it but when I step out the room and return he's on it and tries 2 hang up really...

quick...I know its common sense that he most likely has someone else on the side but I need sum more opinions...

Sounds kind of shady to me. Although, it could just mean that he thinks it's rude to answer calls when your with someone else.
Why not try asking him what's going on. You can do it in a joking way like
"You sure seem to hang up fast when I come around" and then just laugh.
See what he says, if he get's defensive, then he's probley hiding something.

Besy thing is to ask him about it. Maybe it's nothing like he doesn't want to be rude and talk on the phone when you are present (his devote attention only for you!) or maybe, it's what you're thinking. The only way to understand him and get to know him is to talk to him.