If the threads where the other why they would screw on. Wow, I'm not sure I understand what you're asking. If you talking about your pedals coming off then simply tighten them to the appropriate torque. If you damaged the threads because of riding with lose pedals you may need to use locktite to keep 'em in place.
I ride 1000s of miles road and MTB and my pedals NEVER come off. Do you have your chain on the left?
Pedals screw ON if the bearings seize. If the bearings are locked, then the pedals do screw on tighter. That is why the pedal on the right side has a right handed thread and the the pedal on the left side has a left handed thread.
What you describe will only happen if you are pedalling backwards. | 