My pain starts with low abdominal pain which gradually gets worse. It feels exactly like the pain that comes with diarrhoea - which I also get with periods sometimes.
Over the next several hours it progresses to back pain, cramps in my thighs, random sharp pains in my anus that feel like a large metal pole with a point is being twisted in my bum, which nothing I do will ease.

It lasts from 4ish hours to 2 or 3 days.

Medication: If I take it early Nurofen works well. If I can't it does nothing. I used to take Ponstan but it stopped working. Pain killers don't stop the bum pain though.