The most common reason for bleeding twice in one calendar month occurs when a normal period begins on the first or second day of the month, and then another arrives at the very end; because the normal cycle length (from the first day of one to the first day of the next) ranges from 23 to 35 days, this can allow two perfectly normal periods to arrive in the same calendar month.
also abnormal thickening of uterine lining can cause this. this happens when u take only estrogen
containing pills without progesterone
.progesterone thins out the uterine lining while estrogen proliferates it. a balance between these two is essential.
polyps and fibroids can be a factor.
check out your thyroid
if u r getting periods are coming in less then 23 days, consult a gynac and biopsy
should be taken