Weird mystery - can anyone help?!!! Plus scared about taking Danazol

[kumamoto]

Hi, I am trying to figure out the cause of a really weird and sharp chest pain (up by my rib) which I get only during my periods. It's been going on for over a year now...doctors have called it intercostal neuralgia but no-one seems to know why I get it with my periods. No painkillers work, including amitripyline which one doc prescribed to me. Then in an ultrasound test they found small fibroids, which they think might be causing the pain - either that and/or endometriosis. The gynaocologist has now prescribed me with Danazol as the next step. But having read about the side effects am really scared!!! Am also due to run a marathon in 3 weeks time and scared of messing around with my hormones.. But also worried that the marathon will coincide exactly with my next period and this awful pain, which is so sharp I can sometimes barely walk never mind run. Advice????