Im going on a diet

I dont know what to do, today i looked in the mirror and thought to myslf "god im fat". Then i started a diet. But i dont think i am fat. No one has picked on me for my weight and when i told mom she said that i wasnt fat (But moms are surposed to say stuff like that). What should i do?

PS: Ive started making a manga, its pretty cool but i want more people to see it and tell me what they think.