About five or six days ago I woke up feeling tired and weak, as if I might get dizzy easily. Having stood up indoors for a while this actually happened and I had signs of being about to faint. This isn't common for me - I'm only 18 and the last time it happened it was frequent, I was no older than 13 or 14 and it is likely I was iron deficient. That fact and my feeling of weakness makes me think it wasn't just the environmental conditions. My period ended about two days prior to this so that doesn't seem to be a likely cause either.

Since then I've been feeling progressively more lethargic and that I could easily faint if I weren't at home at the moment anyway. It's not very severe, just unsettling as I'm not feeling typical symptoms of illness like loss of appetite. Yesterday I woke up feeling insatiably thirsty. However much I drank I didn't feel much better. This is not so bad today but my mouth is still slightly dry considering how much I'm drinking.

Yesterday morning I noticed a fair amount of blood in my stool and tissue paper. I haven't struggled to go and it wasn't black or painful, so I was surprised to see blood there. I haven't been since so I don't know if the bleed, whatever caused it, is finished or not.

Any ideas what this could be? None of the things I've read about so far seem to quite fit it.