Suggest Treatment For Irregular Menstrual Flow And Missed Period

Hii m 22 yr unmaried.. my weight is 64 kgs and height is 5'3" from last few months i have been observing changes in my mesnstural cycle...earlier it used to be for 4-5 days....then reduced to 3days... with not so good flow...(maybe average...dont know how it should be) and from last 2 months it has reduced to 2 days..with less flow ! this month i have not yet got my periods...it has extended by 14 days till far.... m worried...plz guide me.