I am almost 3 weeks post op. Removal of ovarian cyst with a c-section like cut. Everytime I get up and move around a bit, I get really hot and sweat and dizzy. Almost the same feeling when your blood sugar is low.

Postop evaluation. At three weeks postop you should be feeling better by now. If you are not then a follow up post op visit with your surgeon is definitely warranted to determine that the healing process is going well.
Get checked out. Have you seen a doctor in person yet? If not, do it right away. Today.
After an operation, symptoms like sweating and dizzy and temperature change are suggestive of either infection or blood loss. So it's a good idea to get evaluated right away.