My cat is urinating on accident when she is sleeping help :(?

wow...I thought I was the only one with this problem. I have a gray manx, she is 6 years old and the smartest cat I have ever had. She has the sweetest personality also, her name is Blue....She has what my vet called an incontinence problem, similar to what happens to people when they go into a deep sleep and wet the bed. They kept her overnight (4 yrs ago) but couldn't get a specimen for some reason and at that time I couldn't afford to keep leaving her there. So, I make her sleep on a special folded soft towel that I wash frequently. She doesn't always sleep on the towel so I am doing my blankets a lot. Its a pain in the , but I just love her and she doesn't do it on purpose. Usually it is just a small spot, but smells bad after a while. I would love it if you would write and tell me what you find out about your cat.... thanks so much...