From what I read in your profile, he is a baby? Babies are notoriously messy until they begin to pick corners to pee an poo (but before that, everywhere is game). I’m not sure if this is just something your bunny will grow out of, as this can get better as he matures, or if it is a territorial behavior (which normally happens at around 12 weeks), then neutering when he is ready can be helpful if it is territorial behavior.

As soon as he pees on you, you should just put him back in his litter box right then and leave him be for a bit, so he understands this is not the place to go or to “claim” if he is territorial. If he ends up going in the litter box right then, reward him right away with affection and/or treats, but it has to be done right when it happens, otherwise it doesn’t work. And it takes consistency and persistence. Babies are MUCH harder to train but still trying to train and create the habits you want, are still worth working on as eventually they do sink in as they mature. And again neutering can really help with that. While you are dealing with this, to save your clothes and save on laundry chores, get some disposable puppy pads, and put them on you when he climbs up on you. (Don’t use puppy pads any other way though – with a bunny unattended as they could chew up or ingest).

Here is a link to a past discussion of another member who had the same issue that you may find helpful

https://binkybunny.com/FORUM/tabid/54/aft/143989/Default.aspx