8 weeks, 6 days - "Maybe you're pregnant..." whaaa???!!!

I was in the break room the other day, making a cup of tea and a coworker approached me to ask what I was doing.  We had some tea small talk about what kind and if I like it, you know the drill.  Then he asked if I was pregnant.  What?!  I laughed and he smiled then said, "no, I'm serious."  He's been giving me a hard time about it since.  This was last week and he was back on it yesterday.  I get up at 5 am to go to work and am very tired by the time I'm there so he's decided that's because I'm pregnant.  And I'm drinking tea because I'm pregnant.  And what else... I can't remember, but he's been hitting it hard.  I think he's kidding but I kind of want to tell him just so that he'll stop going on and on about it.  During meetings.  In the hall.  Goodness.  I'm confident I don't look pregnant.  I haven't gained any weight and I'm pretty sure there's no "glowing" going on.  It's just... funny.