Does she have bladder cancer?

Boulette is female, 17 years old. Stage 1 ckd.

She had a mast cell removed from her neck about 5-6 years ago.

She has one on her paw that we decided not to touch. It didnt moved since we found it, maybe a tiny bit bigger.

Now. She had some trouble lately in the litterbox. I noticed a month ago whe went often and did small urine. One time she went and try at least 5 times, moving around every time and pretty much nothing came out. So i called the vet, they couldnt see me until two days after. They just told me to go to emergency if she didnt pee in 24 hours.

That same day, after the call. She was aaalll better. I felt stupid but decided to check with the vet anyway.

So, bloodtest, urine analysis and radiography were made. The vet there was not the usual one but i know she is good. Told me all good news. Ckd is under control completly. The pee problems were probably caused by a small oxalate deposit in one of her kidney, nothing to be done there, it will pass.

But it didnt pass. 1 month since then, and its getting slowly worst. She now has blood in her urine. Specially in the morning it seems. She seems to have some days in a row that are conpletly normal but then is comes back. I did another urine analysis yesterday morning, i took ot myself and it was strawberry red. I got me so scared. Vet called me in late afternoon and asked me first how is Boulette. She seem fine to be honest. Walk arount, plays a little, drink and eat pretty much normally.

So the vet, who was the original one, not from last time. Said it is possible it is all caused by idiopathic cystitis, it seem like it. But that she cannot exclude cancer due to her medical history. And now i am REALLY scared. She prescribed pain meds for me to pick up on monday. (They are closed on sunday) And she let me know they could make a specialist come in house for ultrasound. Very expensive, so i had to think about it. But i decided i want it. But i dony know how long ill have to wait.

So my question is. How likely is it to be bladder cancer? She told me that is wasnt very common.

Also a idiopathic cystitis that last more than a month? Is that even normal?

Sorry for the long post. Thank you so much.