Reading these stories here make me glad I'm the kind of person that goes to the doctor the moment I notice something's off.
But the one exception for that was when, for "some reason", for an entire month, I always started feeling fatigued after only being awake for a couple hours. It felt like there was a pressure in my head, and it felt like there was a rubber band around the top of my head (above my forehead). (Some of you probably know where I'm going with this now.) Thinking it was just seasonal allergies or poor sleep (I had a bad habit of "late to bed, early to rise"), I just toughed it out.
It took until my ears started feeling clogged that I realized what was going on. I'd apparently been dealing with a sinus infection for an entire month, and my ears were starting to get infected from it now. I'd never had a sinus infection without having been sick prior to it before. (I tend to get ear and sinus infections after every cold.) So it kinda surprised me, and it's why it didn't even cross my mind until I started feeling the effects of the ear infection. I think I took 2-3 rounds of antibiotics to clear it up, and I also took a round of steroids to immediately open me up and help me drain.