<human>: Can you condense the text into three sentences or less?

I feel as though I know what the answer to this predicament will be but I figure reading a couple opinions can't hurt.
Reddit, I have less than four months until my 21st birthday. However, I of course engage in underage drinking (although I would say not very often because I'm pretty busy.) I can count on one hand how many times I've been to a bar. A couple nights ago, some coworkers convinced me to come out to a bar or two, assuring me I would not get carded. I went to two bars in my town and neither carded me. At the second bar, I spent a lot of time talking to the bartender and flirting with him. I ended up getting absolutely trashed and may have at some point during the night in my drunkenness, said something to someone (in the presence of the bartender) about being "recently turned 21." Other than that, there was no talk of my age.
Today, I was at the mall grabbing a bite to eat and ran into the bartender. We talked and laughed and flirted. He mentioned coming into the restaurant I work at this weekend to see me. This is my problem: I don't want to become too familiar or friendly with this gentleman because he obviously assumes I am 21. However, we get along pretty well and he's extremely friendly so I am inclined to get to know him better. The thing is, I feel like a complete asshole now for allowing him to serve me alcohol. I know he didn't card me, so maybe that's a fault on his behalf, but even still I of course feel responsible because if anything happened, he could have gotten in a load of trouble.
Are there any bartenders out there that can give me their opinion? How pissed would you be if you found out you served someone underage? Does it happen a lot?
Regardless, I have decided that I don't ever want to go to that bar that he bartends at again (while I'm underage.)
<bot>: I'm underage, went to a bar, bartender served me alcohol and wants to be friends. I feel uncomfortable letting him know I'm actually only 20.