Go down in prey size. Get a small rat and try that. A ball python, specially a male does not need to eat a medium sized rat. He is probably just catching up with his body since he has been eating so much. If they eat to much they will go off eating till their bodies can catch up with everything. I wouldn't be worried unless your temps and humidity are off then that may be causing him to stop eating. But more then likely he is just trying to catch up. Your best bet would be to go down in rat size for the future feedings.