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

Without details, it's a bit of a stab in the dark, but still:

Have you checked your recipe? Some doughs are intended for these paper-thin pizzas, other for deep-dish, almost cakey pizzas. Swap these and your results might be very disappointing.

A few pointers, how to "read" the recipe¹:

• Deep dish doughs typically have a generous amount of fat (olive oil, lard, shortening, whatever) and sometimes cornmeal while thin crust (for purists) ist flour, water, salt and yeast only (or perhaps a tiny bit of oil).
• Dough thickness for deep dish is around 1/2 inch / 1-2 cm, thin crust is, somewhat obviously, about "as thin as you can get it without tearing".
• Deep dish is baked in a pizza pan, while thin crust prefers a pizza stone or steel or, in a pinch, a hot cookie sheet.
• A deep dish needs at least 15-20 minutes, likey 30 or more until done, while a thin crust ideally is done in a few minutes (seconds, in fact, but home ovens don't get hot enough).
• Therefore a deep dish pizza is baked at 425F / 220C (sometimes a tad hotter) while for a thin crust you fire up your oven as high as it will go and use a well-preheated pizza stone to supply consistent heat.

As you write

perfectly baked on the upper and lower sides but still doughy in the inside

I'll assume you are more on the thick-crust side. So a few suggestions:

• bake a bit longer to ensure the middle is done as well. This might require lowering oven temperature a few degrees to avoid burning the top and bottom.
• Make sure your dough is mature - while the edges usually handle being off quite well, the middle remains soggy or dense. (This is true for bread and other baked goods as well.) As I don't know your method, experiment with longer and shorter resting times or do some research on how to recognize the different proofing stages.
• Consider par-baking the crust and adding the filling after 10 minutes or so. As toppings are typically already "cooked", this is fine from a food-safety view.
• Another option is to go for a "slightly thinner deep dish pizza".
• Check the hydration of your dough: If you use a high-hydration dough (=lots of liquid in the dough), a pizza pan with tiny holes to let some steam escape downwards might be an opion. Or use a tiny bit less water.

And as I said, this is a bit of (educated) guessing, based on experience but lacking information.

¹ especially the recipes with the nondescript title "Pizza"...

Until you have the recipe banged out; I would start with just a cheese pizza to narrow down the issues.

1. Do not use ingredients that have high moisture content; (vegetables and fruits)

2. Decide on how you want to deal with moisture on bottom of dough; a use a pan with holes in bottom (special pizza pans).
   b. Douse bottom of pan with olive oil or lard to create an almost FRY environment for bottom of pizza; will keep the bottom of pizza from become moist. c. Pizza stone or baking stones; get it roasting hot at 500+F before using.

3. Be sure oven is properly warmed up before using; I typically have 2 pizza stone @500 degrees; takes oven 1 hour to warm up completely with the stones.