What Causes Stoppage In Periods?

hi so in may 2009 i weighed 155 pounds and am 5 foot 7. i decided to lose weight and dropped to 125 pounds by august 2009 then i went further and dropped tp 115 pounds by april. i lost my period when i started to lose weight and i want it back and become healthly. throught this time i started having binge eating then exercising overly to not gain weight. right now i am 125 pounds but i dont know what to do. please help me