Hi Nicole
Well, until you mentioned the girlfriend, I thought that he might really be interested in you, but now I'm just not sure.
Maybe he's just flirting.
When I was 16 I had a holiday job in a shop. One of the bosses was very attractive ~ and I suppose he knew it. He used to flirt with me, tease me, suggest going out, etc, etc, but he was married and this was just his way of harmlessly ~ as he saw it ~ enjoying himself.
He enjoyed flirting ~ and maybe he enjoyed extra-marital affairs, too. I'm not sure.
Maybe that's what this chap is doing.
Who knows?
Be careful, & be sure of what he is up to, before following anything up ~ especially if you are quite young and / or naive.
Good luck!