Overactive Bladder & OPKs?

I have an overactive bladder and I'm finding it difficult to maintain the 2-3hr recommendation for holding it before testing. Especially after coffee when I have to go every 20min or so.

I tend to get the strongest surge reading in the late morning, even if I've gone once already, and I assume it's because I hadn't peed all night. But throughout the day it's hard for me to go longer than an hour and I don't see much of a surge (close to expected ovulation).

I've got a doc appointment scheduled next month to get my bladder checked but do you think OPKs are not a good method of NFP for me bc of my overactive bladder? I'm just starting out with NFP using the symptothermal method as well as ovulation test strips. Perhaps I need a digital to get a better reading??