yes, yes I know exactly what you mean!
.
I had horrific pain, lying on the floor writhing in agony, taking 2 panadeine extras, that didnt even touch it. (started at around 3 months post cs,)

I used to get mine around ovulation time, then day before and day of AF, my scar would feel like it was going bust open and be red, sore to touch and inflamed.
I went to see a doc about it, was told to stop BFing and go on the pill....never went back to see her again. I kept BFing and didnt go on the pill, I basically just dealt with it until it finally seemed to subside a bit.
I still occasionally get it, more so around O time.
My doc and I are about to start investigating what/why...I have also been TTC for 2 years now with no success, Doc thinks it could be Endo (a common occurrance after CS she says, all the scar tissue and adhesions etc) we will find out soon enough.
I hope you can find out what is causing it soon.
Good luck x