Why am i not getting my periods from about 2...

What is the treatment of missed period :
before starting any medication , you have to exclude pregnancy,then you can manage the cause of your missed period , in some cases it's due to Polycystic ovaries so doctor presripe you a drug such as glucophage with advice of losing the overwieght , it's can be due to hypothyroidism so you can use Levothyroxine drug in doses as presribed by doctor . If all tests are free and normal , it's important to change the life style by eating healthy food , drinking water , Exercising everyday and avoiding caffiene and stress . 
What Investigations can be done in your case ?
you have to do the pregnancy test firstly then ultrasound is a must to exclude PCO . and Thyroid function test such as TSH , also measuring Prolactin level in the blood 
What are the causes of missed peroid ? 
Pregnancy 
Hypothyroidism 
Polycystic ovaries 
Hyperprolactinemia 
Stress and anxiety 
pood nutrition 
Obesity
What you should do ?
You have to visit a gyncologist for investigation and diagnosis