Hi, I am a 21 year old living in Delhi.
I had my last period in February and I am really worried for having skipped them.
During these 4 months my weight has increased from 5-6 kgs, and I experience excessive sweating.
Please advise me what needs to be done.. and are there any specific changes that need to be made in my diet so that my periods start ?
Awaiting your response

There could be dozens of things wrong. Only a proper medical exam by a doctor will determine what is the issue.

Some women have irregular periods, but you need to make sure, nothing serious is wrong.

No periods for a good length of time is called amenorrhea, so you can Google that. I would be wondering about two possible (ONLY SUGGESTIONS) conditions: one is hyperthyroid because of the sweating, and the other is PCOS, polycystic ovary syndrome. You need to see a doctor for either of those and for anything else that is less common.
As for diet, severe nutritional deficiency can cause periods to stop (nature's way of protecting you from pregnancy and keeping as much iron and blood as possible). Extreme exercise can too, in very healthy women.
So you can see there are a wide variety of answers, and there are a lot more.

Absence of Menstrual Periods: Menstrual Disorders and Abnormal Vaginal Bleeding: Merck Manual Home Edition (http://www.merckmanuals.com/home/womens_health_issues/menstrual_disorders_and_abnormal_vaginal_bleeding/absence_of_menstrual_periods.html)

Thanxx @joypuly and @Fr_Chuck for answering :)
Going to doc right away and hope everything's all right.