Why is my pizza doughy inside?
There are lots of things you can try, but the first thing I would start with is weighing your ingredients. Use a recipe that provides ingredients by weight and buy a decent kitchen scale. 

Next I would look at your temperature and set that to be as high as your oven will go(mine goes to 550°F). 

I would ensure that you aren't over topping. I know you mentioned that you aren't over topping, but I still would "top even less" until you can figure your crust out.

Other general tips that might help depending on your situation:


Use a steel/stone
Bring the dough to room temperature
Thin your dough further
Par bake the dough before topping
Proof the dough for longer
Use room temperature ingredients