heat on a laptop is a very good possibility. I dont know how much the cooling pad actually works.. I have one for my laptop just because i had an old gateway way back in the day that had heat issues, I figure for 20 bucks it couldn't hurt. I am not much on laptop gaming, I prefer my trusty desktop for some cs:s goodness
If your FPS are dropping below 10 fps only when your fan kicks in, I would say your heat is a major contributing factor to your loss of fps at that instant. Another thing I wasn't thinking about but may apply, do you use your your ac power when gaming or do you just use battery power, the intensified graphic processing could be lowering due to higher power consumption.
Just a thought though