Why does my camera say memory card error even when I insert a new one?

I dropped my camera and was able to fix it and it was working good for the first day, then the next day it said memory card error. I went to the store and bought a new memory card and it worked for the first 5 hours, then i went to the store and bought another and it only worked for the first few hours again. Nothing was wrong with the camera and pictures but I cant seem to get a memory card to last longer then a few hours now. What do i need to fix?