My question is similar to Pandi's. I have a 19 month old daughter who is nearly weaned--she nurses every 3 days, currently. I have not resumed a period. This also happened after my son's birth. I had an MRI, ruling out pituitary tumors. A progestin challenge triggered bleeding and several months later I was pregnant again. What causes this? Is it possible that I am too thin? I weigh about 118 and am 5'5". Is this hormones? It just seems really strange to me. I have not heard of anyone else with this problem. Is it bad for my health if I don't cycle?