I'm 31 and have always been regular, every 28 days almost to the hour, and my period lasted 2-3 days. In July, my period was a week late followed by a period that lasted 10 days. Then I had 7 days off followed by another 12 day long period. I've just had another week off and now it's staring again. I've had an ultrasound and they saw a think endometrium and a possible cyst on my ovary (common for me). I'm worried sick about what this could be