I think I may have malabsorption.

I eat about double of what my supposed needed calories are, even when doing nothing but sitting around.
I had to cut back my training to the minimum.
With the things I eat (fatty nuts, seeds, fries, cheese, loads and loads of potatoes, noodles and dark bread), I should be obese by now, but I'm not gaining any weight.

If I train or swim too long, I even lose weight (which I can't afford).
I remember being able to thrive and work out on normal amounts of food in the past.

I'm scared to try and find out which disease might have caused this, or whether it has been caused by the antibiotics I was stuffed with, or one of the meds I still have to take and absolutely can't stop taking.

And please no one say "lucky you" or some such, you don't realize how scary and painful it is having to eat so much and still being afraid to weigh even less the next day.
(not to mention expensive)