No, you haven't done anything to shorten the length of your penis. What ever size we are, by the age of 17 year's of age, that's it! Squeezing, pinching, rubbing, even slapping it and stretching it, won't change the size. Some teens/men was just born to have bigger, and thicker penises than others. What ever your DNA, genetics are, that's what you're going to be. I would think a guy with a big penis, probably have a dad, and grandpa, and maybe uncles, that have a big penis! These body types/features usually run in the family. So, just enjoy the size that you are, it's not going to change, and no again! You didn't do anything to stop the growth.