Why don't i get my period? im 16 havent had my period in 18mnths i got it for 6mnths, had it 4 times in that 6mnths and then i sprained my ankle and it never came back i have never had sex or been on birth control

Irregular : Irregular periods are very common in young women. There are other factors that contribute to this occurence such as drastic weight gain or loss, hormonal changes, pregnancy, stress/anxiety, thyroid problems, etc. You should see your doctor for a medical evaluation, and also to discuss the possibility of taking birth control pills in order to regulate your cycle. Good luck.

You need a workup: See your gynecologist. You might have to be on birth control pill to regulate periods.