OK I'm 15 and I started having my period right before I turned 14 and it was irregular of course I was having it like every two or three months but then a little less than a year ago and I lost some weight and was constantly exercising and my period stopped and it still didn't come back again I'm very active and get a good deal of exercise but I'm scared that my period hasn't come back yet

If you have exercised way too much and lost too much weight, that is why your period hasn't come back. You need to put the weight back on in a healthy way and don't over exercise and your period should return.

You should go to your doctor no matter what and talk to him or her about a healthy diet and exercise plan and discuss the issue of your cycle and perhaps talk to a gynecologist. They may administer hormones if the cycle doesn't return within a reasonable period.