Irregular periods !! Help!!?

what is 40kgs? uhm.. kilograms? yep.. you are horribly underweight. Gain some weight and your period should correct itself. I'm 5'1 and I weigh more than you and I'm in my perfect weight range. Get a better diet. I had the problem when I was barely under weight(by 5-7lbs). Talk to your doctor about possible ways to gain weight ASAP. it's really unhealthy and can lead to way more problems than just period issues.