In PCOD, that you seem to have, irregular periods and weight gain are common. You should not get unduly worried about it. For losing weight, restrict the calorie intake and do exercise e.g. brisk walking for an hour or more. Eat a lot of leafy green vegetables - spinach, cabbage - and other green vegetables - beans etc. Do not go for crash dieting and rapid weight-loss. Aim for slow and steady loss.