Ashes

Hey hows it going?
I am 6ft 3" tall and for the last 7 years (im now 25yo) i have not been able to get my wieght above 10st or 140lbs, I have a frame for a big person but i cannot fill it about a year ago I lost wieght and dropped to only 7.4st and since then i have gone back up to just 10, adding more supplements and healthy and even fatty foods to my diet i still cannot raise above that bar. i'm sick of looking at myself and dont know what to do, docters gave me supplements, the hospital dietrition gave me supplements... nothings working
even tried a vince delmonte diet... but i'm currently not working so i couldnt afford it :S

anybody have any advice?