does anyone know this pain?

i have really sharp pinching pulling stabbing pains in my bum right before and during my period. i also have bad cramps and bleed heavy the first day but within the last year, this thing with my bum is happening. its quick pains a couple seconds off and on for at least 20 mins but sometimes goes the whole day. i think it can be pelvic congestion syndrome but i was never pregnant and im not sure where the vericose veins would play a part. internal? so i also thought maybe it could be proctalgia fugax but it happens more in the day while im awake than while sleeping. do these self diagnoses sound close to right or could it be something completely different? can anyone relate to whats happening to me?

Just something I read about.

Rectovaginal fistula - can occur rarely, from diverticular disease of the bowel or Crohn's disease.

It was my first thought.