When I used to get UTIs and treat them with antibiotics, I always ended up with a yeast infection and it was not easy to figure out the difference between the two problems. So you may need to treat for yeast, including cutting out sugar and sweet drinks and bread, etc and taking a probiotic.
There is a condition called interstitial cystitis, which you can read about, but hopefully it's not that. I think there are things you can do with diet and I would look into herbal remedies.
I just looked up nigella sativa, and it treats both UTIs and interstitial cystitis. This is an herbal oil you could order on Amazon. I take it every day as it cures everything right up to death. You want a highly rated organic, cold-pressed form of the oil or pills.