I feel guilty when guys buy me drinks at bars!!?

I have a boyfriend, and I usually have a girls night every other week on Friday night. EVERY SINGLE TIME I go out someone sends me a drink and I don't know if they want to talk to me or hit on me but me having a boyfriend I always say no to the drink. I feel guilty accepting it. Last week a guy took the tab for dinner. The waiter just said, "someone took care if it, ladies" and walked away so I couldn't say no. Should I just accept the drinks people offer me? my friends say its no big deal, and sometimes they accept them for me!! If I say yes to the drinks, Would that be disrespectful to my man?