How can I gain weight?

Im 9stone and doesnt matter what I eat I cant gain weight. I eat all day and im always hungry. why? I could eat a whole frickin 18" pizza loaded with all the shit you can think. 10 minutes ater Im starving so ill eat. Cant stop eating junk stuff either. Haribo, chocolate,crisps,cakes,biscuits the lot.

Why do you want to gain weight!!?? If you're wayyy underweight, I understand, but maybe you should just consider staying the same way, you are clearly a slight and small build! As long as you excersize, eat healthily, 5 a day, and mix in junk food as well! You should be fine, but if you are anorexic, go see a doctor!! x