Michelle,
Your not alone. That happens to me too in situations where i feel uncomfortable (always social) usually based around status...someone questioning my eduction or jobs etc...
I find that humour (trying to think of something funny/stupid that this person whose giving you grief has done)....can help.
Try thinking of something in the near future that you are looking forward too. Night out with friends, date, vacation, event etc.
Try to keep thinking (even if you don't believe it) how much cooler you are than the ppl who are harrassing you, or making you feel uncomfortable).
Distract yourself with something.....
hope these help.
Elizabeth