I'm a bit late to this conversation but.... Your fridge uses about 1/2 an amp per hour of battery while running on propane. It's the electronic controller board uses that power. That means that you use about 12 amp hours per day of battery power for the fridge. If you have the standard battery set-up that comes with the camper you have about 75 amp hours of power (you shouldn't use more than 40 of that's but that a different post) Anyway, the fridge uses 12 amp hours per day, the other "stuff" uses some power too and of course if you have lights on and use the water pump that's all going to use battery power. Long and short of it is that you'll use somewhere in the neighborhood of 20 amp hours per day of battery power which means you could go threeish days before your battery is completely dead. (75 divided by 20) If you're fridge, on propane, only lasts a few hours something is definitely wrong. I'm guessing you already looked into the obvious stuff like making sure the fridge is on Auto and using propane as opposed to DC which uses only the battery. So the easiest thing to do is replace the battery and see if that solves the problem. If not then it's more likely a fridge issue.
Mitch