It’s possible that since he’s had urinary infections before, he may have come to associate his litterbox with pain, and that’s why he’s going elsewhere. This happened with one of my cats who had to have surgery to get some bladder stones removed. He started going on the bathroom rug because the litterbox had bad memories for him, so I bought him a new litter box, and a slightly different type of litter (try Cat Attract, you can get it at most pet supply stores, it’s very good). That was enough to get him to start using his box again. You’ll also need to remove any traces of urine odor from your bed, either by using an enzyme cleaner from the pet store designed for cat odors, or by replacing your mattress. Get a waterproof mattress cover to prevent any further damage in case he lapses again.

Make sure that all of your litterboxes are attractive for him to use – see this link for details: http://www.catinfo.org/litterbox.htm

Make the bed a less appealing place for him to go, by placing a waterproof tarp over it when you aren’t using it. Or, you can spray Feliway spray (from the pet store) on your bed. Feliway has calming ingredients to help prevent him from urinating in areas where it’s sprayed.

You may also want to consider stress as a possible culprit – stress can cause cats to urinate in familiar, comforting places with your scent on them (such as a bed, or in used laundry). Here’s a good article about stress in cats, and solutions: http://cats.about.com/cs/healthissues/a/stress.htm
A routine of regular play therapy can help to calm a stressed cat: http://www.littlebigcat.com/index.php?action=library&act=show&item=playtherapyforcats
A Feliway diffuser may also help: http://www.petcomfortzone.com/czcats.htm

Hope this helps!

If the cat has stones it can’t help doing that….

My first recommendation is to make sure you close your cat out of your room when you can’t watch him.

Second, get a second litter box. He may have bad associations with the old one and sometimes a second box can make a difference. (Keep the old one also. If he starts using the new one exclusively then you can get rid of it, but you may need to keep 2 forever.)

Third, is another vet visit in order? Maybe he’s in the early stages of another UTI?

Fourth, change his diet. The kibble diets, including the Science ZD your vet probably has him on, are often culprits. The best solution for cats with UTI’s is to feed them raw food… there are lots of sites online about feeding pets raw meat. They thrive on it, especially cats.

This last bit is just hearsay, but my friend has told me she has had great luck in resolving the same problem by getting a Feliway Air diffuser. This is a thing you plug into the wall socket and it emits something that supposedly cats can smell. I do not have any evidence other than hearsay for this, but vets are checking it out, too. Might be worth a try.