You have not told us enough to be able to determine the source of your problem. It would definitely help if you can tell us more about the processes you use to make the pizzas, including the dough formulation (recipe) and preparation (including whether you refrigerate the dough/dough balls and for how long), dough weights and corresponding pizza sizes, the type of oven you are using, whether you are using pans, screens, disks or just an oven stone, whether you are pre-forming the pizza skins, bake times, etc. To help you formulate your response, you may want to take a look at the following thread: http://www.pizzamaking.com/forum/index.php/topic,2623.0.html
. Your problem may be somewhat different from what is described in that thread but you will get the idea of how to analyze your problem and what level of detail is necessary to work through your particular problem.
As a preliminary suggestion, if you are using sugar in the dough you may want to omit it entirely (for now) and use a lower oven bake temperature and a longer bake time. If that doesn't help, then your dough formulation or dough management may be at fault.