I don't know what to do

My old boy Tucker has not been doing that well lately. No, he isn't failing miserably, but he seems cold a lot- so is always looking for somewhere warmer to sleep (he now gets piles of blankets next to the heat register). His lymph gland has grown, but he seems totally unaffected by it. The main issue is his peeing in the house. He just seems to go, without knowing it's happening. Then, by the time he realizes it and runs to the door, he's already empty. At least once a day there is a large volume let go. He is weak behind- his back end sinks half way down to the floor when he is just standing. What do I do? Yeah, I know, bring him to the vet, have them test his urine (like they have done myriad times), have it come back "fine", and then what? He should be on prednisone for his gland, but that will really wreak havoc on his urinary system. Any suggestions?