Hi, Thanks for the query. Irregularity in menstrual cycles can occur due to many causes. As three of your urine pregnancy tests were negative, there is less possibility for pregnancy. But as your cycles are irregular, sometimes we may not completely relay on urine pregnancy test. So, once go for ultrasound. If ultrasound rules out the possibility of pregnancy, no need to worry. Weight gain can be due to causes like : - Decreased physical activity, altered dietary habits. - Some women complain of weight gain after using contraceptive pills. -In conditions like hypothyroidism weight gain can be seen. So, with your doctor s advice go for ultrasound, thyroid profile. Possibly this will help in finding the cause for your problem. Start doing exercises, brisk walking etc to decrease weight. Take care.