I have the same problem as you. I went to my doctor and am now on some medication to give my reproductive system a kick start. My doctor said that when your body is under physical or emotional stress, it goes into "fight" response, and puts all food towards protecting itself, which explains why your period stops. Don't worry, apparently it is quite common and is treatable. But please see your GP for a chat & a check up. Good luck xx
i weigh 20 pounds less than you and about a year ago i weighed as much as you and i recently got my period back but i had gone to the doctor and they said that it was because of stress.