What activites bring on the pain? Have you assessed for a TFCC (triangular fibrocartillage complex) leision? It's quite rare but falls onto outstretched hands can sometimes cause damage to the cartillage between the radius, ulna and carpal bones- I damaged my own TFCC a few years ago and specifically got pain around the ulnar styloid process upon putting pressure through my hand and with racket sports like tennis etc...luckily it's settled and doesn't give me much bother now.
There is a special test that you can use to assess for this (unfortunatley I can't really describe it but there will be some stuff on the net), MRI diagnosis is needed to confirm whether there is a tear or not.
It may not be this but thought I'd throw it out there just in case!