What A Weird Day / Driver

Played in a comp today, was shocking no feel around the green at all.
Last part of game on sunday and on the 1st today took driver and hit a 40 yard squirter low and bit left. so convinced myself that there was a crack in it somewhere. so for the rest of the round i took a 4 iron from the tee.  dont have a 3 iron and was a bit dubious on using woods. and for most of the round i outdrove and was more accurate than my playing partners who took driver.
Let the pro hit my driver when i got in back in and he hit it fine. so he taped me up some new ones to try on the range, and all of them i was hitting off the lower edge almost like half the ball below the bottom of the club.

I use a grey or pink castle tee so the ball is high and is sitting about half way above the driver at address so somehow between address and hitting my club is coming to far up. any ideas?? 

Matt ,did you check the tape for ball marks to see exactly where on the club face you were making contact with the ball??

You're getting flat in the swing Matt.  I know that because it's a fault I get occaisionally with the same results.  Many causes, but mine is usually caused by me starting to stand further upright during the swing.