Why do i never feel hungry and never eat?

Hi, I am 19 years old male and I never seem to eat or ever feel hungry, my usual routein is wake up, have no breakfast just go straight to work, i then have 2 toast at 10:30, then i have 2 sandwhiches at 1:30pm, then for the rest of the day i do not eat until i get home and have a small dinner at 9 - 10pm. i hardly drink water aswell its as if somethings stopping me from eating? I am extremely underweight and small for my age. Im starting too feel it is affecting me through work and doing business.