Comes with the territory
Part of being a bartender is being hit on. It comes with the job. When you are around a bunch of drunks loaded with liquid courage, the bartender is often the easiest person to talk to and/or approach, so of course you'll be subject to lots of attention.
Sadly, most people who hit on bartenders are not exactly that desirable (I mean, if they were, why would they need to hit on a bartender working?), so just don't worry about it. Most people forget about hitting on you the next day anyways, you should too.