It's really hard to say what's going on, as I am sure you can guess.

He could have a back or disc injury. No matter what, you need to see the vet as soon as you are able.

If he injured his back, he might show physical pain like being slow when he goes to stand. He might also hesitate to jump up or down from an object.

He might also show medical signs such as involuntary bladder release, paralysis of the limbs or neurological signs.

Some dogs (Especially those with elongated backs) need special care. You will want to provide a step stool for him so he can jump from the bed to the stool to the floor or from the couch. This will help to prevent injury.

Dogs cannot take ibuprofen, tylenol or motrin but some aspirin may be ok.

You can read about the precautions and get dosage information here:

http://www.school-for-champions.com/animalhealth/aspirin.htm

But there are other medications that are much better for pain so only make this a temporary solution.

Let me know if you need more help.