My dog won't stop urinating.

Hello. I have a 10 year old happy and energetic Bichon Frise. Just recently he started to urinate all over the house. He sprinkles on table legs, chairs, wicker baskets, and even in the room I share with him on the bed leg. He mostly does it when nobody is watching, but sometimes he will do it right in front of us! He never did this before and its not like him, he knows better. Sometimes we will take him out and he comes right in the house and sprinkles. He otherwise eats and drinks a lot.We have taken him to the vet and spent at least 900 dollars on blood tests, everything from thyroid, to cancer, to diabetes, and everything came back normal. He was checked for kidney stones but for some reason the vet could not see the x-rays properly. He is still very sharp and doesn't have anything wrong with him mind yet. We do have another male dog but they are both neutered and get along well. A 4 year old Husky. I don't believe its age or behavioural, but I'm not sure. I want to help him but don't know how. Does anyone know what could be wrong with him. I love my dog but this truly has me puzzled?

My dog won't stop urinating.