How Do I Sort Through This Problem?

I kind of met this guy over the net, not a dating website but on fb we both joined the same group and I posted a comment. He liked it and we just started talking. Turns out he lives like 15mins down the road. I found it so easy to talk to him, and we both share strong common interests. We haven't met yet though but he is eager because he likes me. We been talkin on the phone and sending txt msgs. Few days ago he said that we should start dating (I have no idea what that means in the first place, like does it mean bf n gf or wat?)

But I'm worried because my sis works with this girl who claims to be his gf. I've seen that he has commented on some of these girls status, words like love and baby instantly spring out. He also has her sis n mum as his friends.

I saw this and asked him about where we are, he said well together aren't we. I said yea but my sis has been sayin things too me about this girl at work and shes sayin shes like ur bf n stuff. he said don't worry we are only friends. Then he said he needed to go to bed early cause he is gettin up early for a dawn service. Thing is on his 'gf' profile she says that he staying the nite.

I saw all this and thought to ask him indirectly about it, he seemed quick to give me the brush. I'm lost what to do. He says all the right things to me, sayin he wants to be with me etc but I'm not sure. I've got a strong feelin i no wat most r goin to tell me.