I'm caring for my mom that had a stroke and now is showing signs of dementia. Mom constantly thinks she has to go to the bathroom.

There is a condition, interstitial cystitis, which is inflammation of the bladder. It feels like having a bladder infection all the time. It can be controlled somewhat through diet, and there are medications for it. She should be checked by a urologist to make sure she doesn't have it.

In the meantime, eliminate all caffeine (soda, coffee and tea). No alcohol. She shouldn't eat citrus fruits, spicy foods, acid-y foods (tomatoes), black pepper, and a lot of other things. They all irritate the bladder.

Check out the IC sites online. They offer much good information about this condition and how to control flares when they happen.

You say that she has had a physical. Did she specifically see a urologist? Because it very much sounds as though, in absence of any bacteria, she may be having an irritation called urethritis. It can come with a thinning of the mucous membranes that protect the urethra, and can make a person feel as tho they have to go, pretty much continuously.

In the absence of anything like this, and if this is a sort of OCD thing, sometimes a low dose anti-depressant works well for people.

I would continue to follow this up with good MD referrals.

I would make sure that she wears Depends 24/7(just in case of an accident)and then just try and keep her on an every 2 hour to the bathroom schedule.
When she says she has to go remind her that she just went and that you will take her again when it's time.
It sounds like her brain is stuck in a loop which can be normal for someone with a broken brain, so try distracting her to doing something else more fun.
It could also be an OCD behavior which is also common with folks with dementia. Thankfully there are medications for OCD behaviors, so you should talk to her doctor about that.
I wish you and your mom well.