CAN't STOP>>> HELP ME

Well report cards just came out, yet somehow I don't feel too happy.  All my  grades for the second quarter were A's, but I can't seem to be excited.  I have six A's and one B for semester grades, most people would be thrilled to see that on their transcripts, yet I am feeling kind of bumed out.  On top of all this I don't know what to do about my eating.  I come home from school every day to an empty house.  So then I eat (for the first time that day) everything I find appealing, and then I purge (for the first time that day).  Often this will happen one or two, sometimes three times in the hour and a half I am home alone before my sister and father come home.  Then at around five we eat supper, after supper I go shower and purge (usually for the last time that day).  Then I will do everything else I need to do that night, and I normally have a snack or two later.  This happens to me everyday, and I can't stop!  I AM TERRIFIED!!! My chest hurts, I am brusing, my hair is falling out, my nails won't grow anymore, I'm in constant pain, Yet I CAN'T STOP!!!