Are you..... ??

A guy is in line at the supermarket when he notices that a rather hot blonde behind him has just raised her hand and smiled hello to him. He is rather taken back that such a looker would be waving to him, and although familiar he can't place where he might know her from, so he says "Sorry, do you know me?"

She replies, "I may be mistaken, but I thought you might be the father of one of my children."

His mind shoots back to the one and only time he'd been unfaithful. "Holy crap," he says, "are you that stripper from my bachelor party that I screwed on the pool table in front of all my friends while your girlfriend whipped me with some wet celery and stuck a cucumber up my ass??"

"No," she replies, "I'm your son's Math Teacher."