Reading this with interest but a sinking heart.
My DD now 16 has had increasingy bad periods over the 3 years since she started, & at first I put it down to inheriting that gene from me.
Attila you in fact first suggested endo but as she was only 14 at the time I thought it was far too young but it stuck in my mind & now we eventually have a diagnosis, (after many drugs, A&E admissions & totally wasteful appendectomy ) I wish I'd heeded your advice & saved her 2 years of agony 
She is under a lovely older gynae chap who she trusts, which is a big deal for her given that she has been mucked around hugely by medics & even been made to feel she is making it up.
She is on the mini-pill, which has helped the pain mostly so she's off the fistfuls of painkillers but until the cysts are gone (which may mean losing one of her ovaries) we won't know what's giving her more gyp.
She has started 6th form & is keeping up for now, but has missed loads over the last few years so her predicted grades are low & she's set her heart on Uni.
So given that its a bit soon to whip out her uterus what would anyone suggest anthing else?
It is hard to keep her spirits up some days as I don't have the answers and I don't know if we ever will, the thought of her being like this for the rest of her fertile life is heart breaking. 