Why Am I Not Getting Periods For The Last 2 Years?

Hi, i am 22 yrs old unmarried..i'm not having periods from last 2 yrs..i am not anaemic n having physiological goiter but T3, T4, TSH values are normal..i have consulted many doctors they diagnose polycystic ovaries and i have taken medicine they prescribed for almost 1 yr but no benefit..im not obese no insulin resistance..ultrasound shows no abnormality..what should i do?