If you are breastfeeding, prolactin (the hormone which brings milk) will prevent you from menstruating. That's why breastfeeding is sometimes called nature's birth control. If you are not breastfeeding, and not pregnant, then I am going to assume you're a bit overweight and insulin resistant. This is pretty common among desi people, both male and female. Sometimes the person isn't even overweight but they still have an imbalance. One easy way to check is to see if you have a disproportionately large stomach as compared to your hips.
Excess insulin causes a slight excess of testosterone which can upset your cycles. The more overweight you are, the more excess insulin your body produces.
1, So the first thing to do is start doing some cardio daily to reduce weight. Try something like walking around the neighbourhood with the stroller. My mom has a calendar on the fridge and everytime she goes for walk, she puts a sticker on it...kinda funny but it really works. If that's hard, just start by doing 5 minutes a day and try to increase your exercise by a minute everyday.
You should try to eat whole foods. That means try to eat foods as close to their natural form as possible. Don't go by calories. For example, diet coke has zero calories but it is so far removed from anything natural-it is just a bunch of chemicals. Also, recently it was proven that diet coke has chemicals that, ironically, promote fat retention.
Eat low-glycemic foods. Eating something like pizza will drive up your insulin levels for several hours. Basically all 'maida' foods like croissants, chips, pasta, etc. are high glycemic. Avoid them. If you must have something starchy or sugary, combine it with fiber, protein, or fat to slow down the rate of sugar absorption.
Basically, following the dietary advice normally given to diabetics will help you even if you are not diabetic because insulin plays a role in both cases. The most important thing to start doing is moving.