I have had this problem too since my mid teens. I've tried eating right, dieting, starving myself etc but if something triggers it (like years ago when I was trying to diet, some online 'friend' started picking on me, said 'go eat a big chocolate cake'. I was in tears for days, even exercise didn't help and I fell off the wagon, started eating junk food again) I go back to eating the wrong things. It doesn't help that I've been a fussy eater since childhood either.