I am not tired enough to sleep but I am not awake enough to fully concentrate.

It has been going on for 3-4 days. Am I burn out?

Might not be burn out.

Could be depression, nutrition problem, ... Thousands of possibilities.

There are these weird doctors who get off poking people's illnesses and try to solve them.

Go speak with them, let them do the poky magic.

Maybe you drank coffee in the evening or smoke before going to sleep? I had this issue because my brain was overstimulated, so I had to stop drinking coffee after lunch and I had to stop smoking 2-3 hours before sleep