Many things: Could be normal variation--cycles aren't always exactly the same. Count cycle from beginning of one period to the beginning of the next. Cycles should be between 21 and 45 days during your teen years. Write down the dates. If your periods are outside this range or becoming more irregular, see your doctor.
Answered 8/30/2013
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A doctor has provided 1 answer
A doctor has provided 1 answer
A doctor has provided 1 answer
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