Why isnt my periods starting?!

Why isnt my periods starting?

I didnt get my periods this month and Iam not pregnant, I went to the doc and he gave me Duphaston 10 mg 2x daily for 5 days. Now its been 5 days since Ive finished my dose and I still didnt get my periods. Why is this happening? And although Im 20 yrs 5ft 3 In, I weigh 36 kgs and Iam on anti depressants from past 2 months. How can i get back my periods if Duphaston isnt working? plzz help me...

2 weeks ago
but my periods were never irregular, its the first time, and the worst part is my mom doubts iam pregnant though im not:(

Does the antidepressant have an effect? Could you have a lot of stress that is causing you not to get your period? How about another illness? I'd talk to you doctor or get a second opinion.