I've not had anything as structured as a pain diary, but I have been asked about pain on a scale of one to ten at varying times (I have stage 4 endometriosis). I was asked how many days I had pain before a period and how I'd rate it, then during a period (did it vary - what was the worst pain and what was the 'general level') and what it was like the rest of my cycle.
I did find it useful as it helped me focus on comparisons between the different levels of pain I was experiencing. Because pain is something you don't remember that well (which is why babies have siblings...!), it helps to have a concrete scoring system to measure it with IMO. If I'd had a more involved problem, I'm sure that keeping a pain diary would've been something that helped me.
(And just for info, worst pain during a period - 10, worst pain during labour - 8-9...)
Hope that's sort of what you're after - I know it's not quite a questionnaire or a diary.