If your cat does have a urinary blockage, he will have to get it taken care of immediately.
My cat had it years ago. We didn't know what was wrong with him at all. He would try to urinate in weird places, but nothing would come out. This went on for a day or so. The next morning I woke up to find him almost dead in my basement. We rushed him to the doctor who had to catheterize him. He was just about in a coma and he was going to die, but thanks to my wonderful veterinarian, he pulled him through and I was more aware of urinary blockage. He was on special food for the rest of his life. (He lived to be 17).
You will need to do something FAST. Time is of the essence here. Believe me, you will regret not doing everything possible if you wake up tomorrow to a dead cat, which could very well happen. He is slowly poisoning himself, and he will suffer. Call your vet and tell him of the symptoms and tell them that you'll need to be put on a payment plan but that this is an emergency.