I haven't had my period in over five years, but two of those years I suffered from anorexia. Is my period ever going to return? I am still under 21..

Not sure. It may not. The changes which occur to cause someone to stop having periods sometimes last a long time. Even if behaviors change there can be a long lag until the body gets itself organized (sort of speak) to have periods again. This can be very serious and can cause some serious consequences to your health (weakened bones, heart disease) and you should see a specialist to treat those aspects, which are more important that the actual periods coming. Time in this case makes a big difference and you want to get treated asap!