You aren't alone. When I was 13, I was asked by a classmate when I was due. I hadn't even had my first kiss yet!
And last summer, I took Wally (my boyfriend) to the emergency room, as he kept getting sick. We'd actually been joking for a month that he was carrying my lovechild, and how horrible morning sickness can be (this was when it was only once a week he was getting sick). Then he started getting sick more frequently, and one Saturday, he was sick several times in an hour.
Once he was back in a room and undergoing tests, I was asked at least six times by four different people if I was pregnant (three nurses, and the doctor). They thought he was maybe having sympathy sickness, until I told them that if I was pregnant it was news to me, but I'd be happy to take a pregnancy test if it would get them to STOP ASKING ME!