I have a 4yr. Jack Russel/Beagle cross that went thro heat and now is peeing on the floor. She seems to have to pee every 3 hours. I am sure this is medical. What can cause this?

There are many reasons that can cause frequent urination, bladder or urinary tract infections, bladder stones, kidney failure, cushings disease, high calcium in the blood, Pyometra, or an infection of the uterus (often seen in older unspayed females), Pituitary gland problems. You can see that if your buddy is drinking too much water, he may have a serious condition. It's also possible that the problem is as simple as a canine urinary tract infection, which is easily treated. As you can see this list can go on and on, if you think it's a medical problem then you NEED to take your dog to the vet.

Is there any reason why you haven't gotten her spayed yet? Please consider it, she will be much healthier in the end. There are millions of dogs dying each year in North America due to un wanted pregnancies, which can be easily avoided.

I have her scheduled to be spayed but can't until this is cleared up... Thanks Back to the vets Monday with this list.

Sometimes the females can get an inflammation in the vagina that makes them feel as if they have to pee all the time.
Definitely have your dog checked for this and also for a urinary tract infection. If the dog has either infection, don't leave it untreated because it could lead t lifethreatning diseases like pyometra (uterus infection) or infection in the kidneys.
Get the dog to a vet as soon as possible.
(I was a Vet Tech for 12 yrs.)