How long did you mix it. I let in run my kitchenaid for at least 10 minutes. I've found it does better with a one and a half to two hour rise. A few cooks ago I started dumping the dough onto my working surface by turning the bowl upside down instead of trying to grab the dough out of the bowl by hand. It seems to really help keep the dough airy and stretchable. I've also found that 3.5 cups of flour is all I need. It looks like its going to be too wet at first but after
@5onia mentioned letting it work longer and letting the the gluten do its thing the dough is perfect if you let it mix long enough.
I usually use water as close to 110 degrees as I can and let my yeast sit in the warm water for a minute or two before mixing it in with everything else. I think this helps jump start the yeast.
Once the dough is out of the mixer, separate it into 3-4 dough balls. It is way easier to separate it at this point, then let it rise. I usually turn my oven on at 170 for 1-2 minutes while I am mixing my dough then turn it off. This heats the oven slightly (not much) and seems to create a better environment for the dough to rise. I put my dough into individual bowls, cover in plastic wrap then put in the oven to rise.
Also, I highly suggest NOT using a rolling pin. A rolling pin will push the air out of the dough and make it very rubbery and unstretchable almost instantly. I tried rolling one to see what would happen two cooks ago and that dough ball went into the trash. Last night I divided my dough into 4 dough balls instead of 3 and it seemed to be easier to stretch. My pizzas might have been a little smaller in diameter, but not by much. The dough was a little thinner and my pizzas turned out great.