I haven't experienced this but I did notice when I was on nortriptyline that my need to go was greatly reduced and thus there was greater volume. Even if it's not a specific med it could be your pain meds are dampening other sensations. On the other part of the problem, do kegel exercises if you can.

My concern for you would be holding too long and getting a UTI. If you don't have a lot of sensation you may not notice so much if something is amiss.

IMHO - it might be a good idea to make a plan to go 3 times a day (morning, afternoon & before bed ) whether you feel you need to or not. And I know this is so basic but making sure you're hydrated will help keep things clear. I wouldn't want you to have anything else to deal with....