Originally Posted by Aniroc
The vet tried to give him a steroid pill once (for a URTI)
For some reason I missed this part before. Do you mean a UTI, as in urinary tract inflammation, or are you referring to an upper respiratory infection? If it was a UTI, that could be a very big clue. In that case, it's of utmost importance that you feed him wet food. This could be a case of cystitis, which might be making it painful for him to pee.
There are a couple of main reasons for cats to pee on things like couches or beds or clothing. One is because their owner's scent is concentrated there, which is comforting to the cat when they're feeling lousy. The other reason is that this scent, even after washing, still has a bit of an ammonia base to it, which can instigate some cats into marking over top of it. I would be more inclined to think this is a comfort thing for your cat rather than a marking thing. Definitely get a urinalysis done.