by rbf on Sat Dec 29, 2007 3:25 am
You first need to be getting reasonable regular monthly periods.
A common reason for widely spaced periods is abnormal thinness. Female athletes with very low body fat often do not have regular monthly periods.
If you do have a normal body fat level, then it's likely time for a medical consultation.
Being 21, your chances of having children are quite good provided you get to normal monthly periods.