Ok young lady. It is now 3:45 am my time. You have to start flying to Canada (or at least my neck of the woods to drink). I just spent the night out explaining to a couple of friends exactly what is causing you stress! Granted I might be a bit jaded and generally uptrusting but I think I said at least 3 times tonight that just because a woman is drinking alone at a bar doesn't meant she wants your smelly self creeping up beside her.
Sadly that didn't make me very popular (I think I might hve had my "man license" revokeed!) but I'm happy to see someone post exactly what I was debating all night!
I think when guys see girls alone at a bar, then see a big target... I usually stay clear of bars, but yeah use Helter's line, that sounds like a great turn down line!
Not that you don't have the right to turn down anyone who comes up to you, but bars are generally for socializing, not just alchohol aquisition. when someone goes out alone to a bar, it's usually because they want the company of others rather than drinking alone. It's not always true, but often enough that someone like you is the rare exception and unless you are wearing a sign, people have no way to no not to talk to you until after they talk to you unless perhaps you flag them off with some semaphore or mace them as they approach.
!!! 
Sadly that didn't make me very popular (I think I might hve had my "man license" revokeed!) but I'm happy to see someone post exactly what I was debating all night!
Sweet dreams!