runDirtyrun wrote:
When was your last physical? When was your last blood tests? Any dietary restrictions?
In order to help you, we need some ideas of what your workouts are like for a week or two, how much training you are doing, what your times are like.
No, we really don't need to know any of that stuff. Here's the bottom line, OP: You probably aren't getting enough calories in your diet. It's very bad for you. It will mess up your body and lead to low bone density, osteoporosis, and stress fractures.
You may not have a full-blown eating disorder, but it's likely that you've got some kind of "disordered eating." Usually the pattern with high school girls is not eating enough calories, not eating enough fat, and not eating enough meat. More of all of that, plus maybe a multivitamin, should sort things out quickly. If it does not, see a doctor who works with female runners and who knows this stuff, since there may be some underlying health issues too.
Really though please don't blow this stuff off. Female runners with very irregular periods are almost twice as likely to get stress fractures.