car will not move in reverse.

car will not move in reverse. So i have a 97 dodge caravan 2wd 3.3ltr i was backing out of my driveway and it hesitated befor moving but moved about an hour later i got in and put it in reverse and it would not move. Pressed on the gas a little and it still wouldn't move all other gears work and fluids were checked and are good. I can feel it shift into reverse but no movement and when the gas is pressed it rev's and sounds like it puttered like it was about to backfire. Any ideas?