Hey, for the past two years i told myself that i was buff, and fit. The reality of it was that i was not. I was a skinny guy. I weighed 140 pounds and i was 5'11. I thought I ate a lot but i did not. Recently, I came across a diet called GOMAD. Basically, you are to gradually drink a gallon of milk a day. I can't force myself to drink that much milk so i tried for 1/2 a gallon of milk a day. Keep in mind that I felt it was impossible for me to gain weight. I've been on this milk and resistance workout for 1 and a half months now. At the end of my 11th grade, I weighed 145 pounds. 1 month later, i weigh 165 pounds. My whole family and I were shocked to see this rapid growth in weight. I've been getting more female attention and my friends have noticed my muscle growth. It truly works, you should try it!
P.S. If you don't workout, you will just gain bad weight.