Do you feel "icky" all the time?

"Feeling icky" could mean a number of things. Let's summarize it like this - feeling tired most or all of the time, experiencing brain fog (hard to think and concentrate), feeling indecisive, depressed, lethargic, unmotivated, half-asleep, insomnia, upset stomach, poor appetite, etc.

To be clear, I'm not talking about just one of those feelings. I'm talking about several, most or all of those feelings, and maybe more besides.

There could be a number of causes for this general feeling of being "off colour":