I experience extreme depression at certain times of day, have a history of self injury, milder form of eating disorder. is this a sig of mental illnes?

See below: Not "mental illness". But certainly depression and another psychological diagnosis. You will benefit from seeing a psychiatrist and therapist.

You know answer: You have described yourself as having a long history of problems with mood and behavior that have caused and are causing you to function much less well than you would like. Impossible to say what, exactly, is going on with just this informatoin, but you definitely deserve the chance to find out by seeking professional help.