I had a sudden attack of pain like that, was so bad I went to ER because I had no idea what was happening. They were not helpful but I went for ultrasound which revealed cysts, endometriomas, fibroids. The pain went away in about 48 hours, though I still felt very fatigued. Doctor was being dismissive but when I asked whether it could've been a ruptured cyst, he said yes, especially if the pain was sudden.

Yeah sounds like a ruptured cyst to me. I once walked round with a 5cm haemorrhagic cyst for 3 days before I went to hospital with it, I'd been in the pub drinking and playing pool like it was normal, and that was exactly how I felt. I think with endo you can learn pain so when it's what someone without endo would be panicking about and going to hospital for you just think ok this is just a bad pain I'll be ok but really your perception of what is worrying has become distorted by what you've got used to feeling on a daily basis. But, that doesn't mean it's not worthy of attention. I then spent 3 days on a morphine drip while they deliberated about removing it. It shrunk on its own so it was fine but people lose literally litres of blood in life-threatinging ways through ruptured cysts- like all other aspects of endo they are slimy, fake, lying bastards whose true nature is only revealed by a surgeon's intervention. My whole pelvis was full of old blood that I then painfully re-absorbed while lying in hospital. Go and get yourself looked at- cysts are not trivial, however much they try to make you think they are. There is always the possibility of infection too.

Cyst or ruptured cyst?