How do I gain weight?

i eat all day, and seriously all day. eat around 2900 to 3100 cals per day. but i dont gain any weight at all.! what shoud i do to gain weight?
i live a very active life. m a football (soccer) player. and i work out regularly.. but i still gain no weight.

i do not in any case feel weak, i m strong. and the fastest.
i dont get sick either. but i look skinny.

i just want to look better!
How do I gain weight?
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