Hi, My Dog Is 9 Year Old Shitzhu. He Was

Hi, my dog is 9 year old shitzhu. He was bleeding from the penis a couple of months ago. The Vet put him on an Antibiotic and told me to get him fixed, which I did. The Animal Hospital also mentioned it could be prostrate cancer or some kind of Tumor and by getting him neutered would help with shrinking of the mass/tumor.

He seemed fine for awhile and now he is peeing on my bed, on the couch and pooping on the floor. He never did this kind of stuff ever.

What should I think of this? Please help!
Thanks,