This is eithe one of two things Lea.
a) He's a nice bloke, who, without realising, has crossed the line. One of you needs to be the adult and agree no lifts, etc.
b) As others have said, he's after a quick fumble with the new girl. If this is the case, don't expect him to ditch his missus for you, and be prepared for rumours circulating about how you threw yourself at him, and went psycho when he refused etc.
Either way, unless you nip this in the bud, you are going to end up looking like a dick. You'll either be the psycho that is throwing herself at the barman, or the tramp who'll get nailed by anything with a cock.
I'm not trying to be harsh, but you sound young and naive, and this is the way the big bad world works I'm afraid.