What Causes Irregular Periods?

hi i m 19 and unmarried, i had my regular periods since age12 but for the last two and a half year has become irregular , my doctor prescribed me "duphaston" and then "progyluton" to regulate them but still irregular, i m much worried, my FSH level is 98 miu/ml , LH is 37 miu/ml and estradiol is less than 20 pg/ml , my FSH LEVEL is too high ,R these symptoms of menopause or pcos ? which medicine should i use to regulate periods ? how my FSH level can be reduced ?