Sorry to be so blunt - but that is why I came to the women's forum! I hear of women not having a period when their body fat gets too low - but I seem to have the opposite issue. I notice it more when I first start training again, I will start my period about 5 days early, and still have my regular cycle. I have been training for 2 years now & at peak volume times it still happens. I am on the pill & have been for a very long time. I am not dangerously low body fat, I'm around 13.4 % and look more sturdy than lean.
Anyone else experience this phenomenon? I have talked to my OB Gyn some - but usually they just ramp up my perscription.
I'm on the pill, too and what I've noticed is more breakthrough bleeding when I'm training heavily, but I don't know if it qualifies as starting early. I'd talk to a female specific sports medicine person, if you can find one. MY Gyn's pretty clueless when it comes to anything tri-related.