If you ran over something, it is possible that you damaged some of the e-brake system or something is jammed up into a component in the e-brake system.
If it were my car, I would (safely) jack the rear up, put it on jack stands and visually inspect the cables, etc. on the e-brake system. Look for damage, or something foreign jammed into the cables or other components.
If you can't find anything wrong, have an assistant operate the e-brake from inside the car and view the operation of the e-brake cables, components, etc.
And yes... you are correct, if the e-brake is on and dragging you will wear down your rear brake shoes and possibly damage the rear drum (itself).
If it were my car and right now I do not have time to troubleshoot it, I would temporary disconnect e-brake at rear brake so not to unnecessary wear shoes. Just for the time being try to park on even surface.