Bladder training - increase holding capacity - spasms are painful

Looking for guidance from others who have had to regain bladder function. I had a bad case of Radiation Cystitis along with hemorrhagic bleeding that sent me to the hospital multiple times for blocked urine flow due to clots, the last time being end of Jan 2023. After 20 sessions of hyperbaric oxygen therapy last year, and 50 sessions this year ending late March (second round needed because of recurrence), I have been completely free of any bleeding , even a tinge, since early May.

But, in my case, possibly because of overdose of Botox for overactive bladder last year, or possibly because I had radiation cystitis, I had to have a supra pubic tube inserted to avoid repeated self catheterization and rupture of fragile blood vessels. It did make life easier and made doing hyperbaric oxygen therapy easier. I am at the point of trying to get my bladder back to holding urine as recommended by my urologist.

The difficulty is that I get these extremely painful bladder spasms starting after about 100 ml of urine holding, and then periodically, until I cannot take it any more, meaning perhaps 6 or more, each lasting up to 20 - 30 seconds. When they become too frequent, usually by around 90 minutes or so, sometimes longer, I need to release the pinch clamp on the SP tube. I have held up to 200 ml, but it is painful to do it. My doctor says over time this should resolve and that it can take 6-9 months to recover bladder capacity. Meanwhile, even during a spasm I get no urine passing normally, even when relaxing the bladder. This is much different than when I had Overactive Bladder, before all this, and release during a spasm would certainly wet my clothes.

I wonder if I should only hold to the first spasm and then release urine. Or may be a combination of both approaches, alternating in some way.

I have started taking Myrbetriq, in the hope that it will enable bladder expansion, yet I do not know whether the spasms are due to bladder muscle stretching (I had 6 months of catheterization / SP tube), or due to sensitivity of bladder lining to urine. I will be checking in with my urologist later this week.

Appreciate comments from those who might have lived through this.

Fiddlecanoe
Can you drink decaf coffee or did that bother you also?

At first I thought switching to decaf coffee would solve the problem, but it didn't. Spasms persisted. I was surprised that tea didn't bother me. Based on occasional experiments, I have found that I can tolerate coffee now, five years later, but I still drink tea almost exclusively because it doesn't require cream and sugar, which I'd rather avoid.

Although beer makes me pee more, it certainly calms down the spasms.
I can actually hold it better without pain.