I have so much self hate because my self image doesn't match my mental image
How does your self-image differ from your mental image?
I think I'm skinny and charming, when in reality I'm pretty much the opposite.
It sounds like you have a case of body dysmorphia on top of self-esteem issues. You should have it checked out by a psychiatrist or it might lead to prolonged health problems down the road.
I don't think I have that, it's not too bad and I haven't harmed myself.
That's great you still feel fine, but it's just going to develop further. I believe it would be best to seek help right away, so it doesn't get any worse. You deserve to love your body for what it is.