Oh golly, my heart goes out to you. I had a chronic UTI years ago, long before all of the antibiotic resistant bacteria came on the scene. It was awful but finally, after 3 urologists and an actual diagnosis, they nailed it. I was on antibiotics for a year but it worked! I truly hope your doctors will continue to pursue this situation for you.

I found some discussions on Connect with other members who also have Chronic UTIs and have shared their experiences as to what they’re going through, treatments and pain relief. I’ve posted links to the conversations below.
These are in chronological order with the oldest first. There’s a small window under the opening statement where you can reverse the order to the most current conversations.

Recurrent Urinary tract infections.
https://connect.mayoclinic.org/discussion/recurrent-uti/
~~~

Recurring bladder infection. What can I do?
https://connect.mayoclinic.org/discussion/bladder-invection/
One other article that might have some merit is a paper in PubMed by the National Institute of Health. It discusses morganella morganii and possible treatment when it’s drug resistant. Most of the article won’t be related to you as it discusses systemic infections. However, down near the bottom where it says, Conclusion, it does mention drugs in a combination form that might work. Worth reading anyway.
https://pubmed.ncbi.nlm.nih.gov/34193353/
To help with the discomfort, make sure you drink at least 6-8 glasses of water daily. I know it seems counterintuitive but it really will help keep the bladder flushed and reduce the bacterial load. (Make sure the toilet bowl is cleaned with Chlorox or Lysol frequenly)

Have you tried any of the OTC drugs such as AZO, Cystex or Urinex to help calm some of the pain?