yes, overeating is a symptom of distress, but it is also more complicated than that.
I agree, eating disorders are caused by relationships (especially the relationship we have with ourselves).
Feeling very bad about ourselves can cause us to overeat and sabotage ourselves.
Often we judge ourselves by our exterior but what is more important is who we are as people.
Why not pluck up the courage and confidence and ask her now?
(Asking girls out sounds a bit like a diet, we'll do it tomorrow or next week).
Even if you feel shy, stupid, ugly and worthless that may not represent reality. I have felt those things myself. Most were based on my perceptions. I allowed my perceptions to affect my life very badly. Putting pressure on yourself to be that ideal person can also leave you feeling worse about yourself.
After reading your posts, and I know you didn't ask for advice but, I think you should talk to someone. I think you are extremely critical of yourself and I think this has the potential to negatively affect your life.
I think sometimes we can waste so much energy on berating ourselves we forget to live life and enjoy it.
Good luck for talking with the girl from your school.