Is there a medical condition that makes me fall asleep during boring things?!

As I was growing up I started to get to the point in church and school or my dads prayers at the dinner table where I would fall asleep almost instantly. I would fight it like crazy, but the best I could muster would be to be doing the head rock where I would pass out and when my head fell I'd wake up and then repeat, over and over, until I would lay my head on something and sleep. I think there has to be a medical reason for this because it was not simply me trying to sleep because it was boring because even when I tried to tell myself it was interesting, or even if it was, people talking for a long amount of time in situations like that just puts me straight out. I went from an A/B student to passing with anything from an A to a D at times. At church I would always be found in the back row asleep... So if it helps any, I am 22 years old, 6'1 and 269 pounds. I play games mostly for entertainment. If there is any other information that seems relevant please feel free to ask. Thanks in advance for anyone who seriously looks into this. My previous doctor had no idea what this was.