Cats are wonderful animals, and I've shared my life with many an amazing one, but they're not really capable of much thought. If yours is peeing on your bed every so often, it's for one of three reasons:
1. He has a UTI and suddenly had to go (which you ruled out)
2. The litterbox isn't clean enough for his standards
3. The bed smells like you and he decided it should smell like him
You can try working on #2 -- some cats really do have standards that require daily cleaning. And everyone says they do it, but no one really does. so, you can try starting there.. it could make the difference.
If it's #3, you can't really convince him not to pee on your bed, unfortunately. That is, you can TRY, but it'll be REALLY tough. To do so, you have to be on the scene EVERY SINGLE TIME he STARTS to pee. You hiss or make some other freaky noise, sweep him off the bed in a fast but non-injuring way, and basically scare the crap out of him as soon as he thinks about it. After enough times of this, he'll think of doing it and then run away instead, in a conditioned response. If you miss his speed-of-thought one time out of 10, he won't stop.
The true solution? Close the bedroom door. The cat is only allowed on the bed when you're there monitoring him. If he decides to continue, you decide whether you can live with keeping him out of the bedroom permanently or washing your bedding a lot.
I wish I had better news. Some cats do grow out of this, and neutering him MAY help. Honestly though, man, they're cats. Where we think they should pee isn't something they think about. Ever. Good luck!
P.S. Add baking soda to the wash.