you may want to check your blood pressure and heart rate
You would use "fall" because "to fall" is the infinitive and you use the uninflected version. "Fell" is the past tense of "fall," but you are not using past tense here. "Fell" can also be a transitive verb meaning to cause (something else) to fall. If you chop down a tree, you fell the tree, but the tree falls.
Once upon a time a boy wasn't looking where he was going and fell down a well. No..wait. He just fell down, well, the point is he died. The end.
I fell down and
possibly... but that can happen any year 2012 BC is when the Mayan kingdom fell down
Lynn makes pie and got it on loads of shelves and the shelves fell down and covered her with pie.
Bella swan is a human girl who fell in love with a vampire
Jack fell down and broke his arm.
some one shot it and it fell down
Elena, the main character in vampire diaries, lives in a place called fell's church name after the founders Honoria and Thomas Fell. If you haven't read the books then you should they are really good!
The past tense is fell down.
he fell down the stairs he fell down the stairs
the walls of Jericho fell down