when I was around 18 or 19 years old, my weight was 125 pounds at 5'10, so I know your experiences, but overall the answer is to eat more. back then...
The decisive thing is not the reality of the object, but the reality of the subjective factor, i.e. the primordial images, which in their totality represent a psychic mirror-world. It is a mirror, however, with the peculiar capacity of representing the present contents of consciousness not in their known and customary form but in a certain sense sub specie aeternitatis, somewhat as a million-year old consciousness might see them.