Hi, I have a GE range and the oven is not heating properly. I baked a meatloaf last night and it took too long for the meat to get to the proper temp. Today, I tried to bake a pizza at 400 (just like last Friday) and the pizza looked like it had only been in for about 2 minutes at the 13 min mark. I turned up the temp to 450 and the cheese began to melt and brown after about 10 min, but the bottom of the pizza was still rubbery and uncooked. When I open the oven, I do not feel the heat like I used to. Also, only the top of the pizza showed signs of heat, not the bottom. Any ideas? This oven is 20 years old this month.