Why am I not sleeping?

You sound as though you're too stressed out by not sleeping to be able to sleep. I'll suggest a few things with no guarantee that they'll work.

The sleep specialists always say if you're not asleep within half an hour/an hour (I forget which) you should get up and do something relaxing until you're ready.

Also their advice - get off the tea, coffee and anything with chocolate in it (they all have caffeine). Also don't have milk products.

Turn mobiles/computers, etc either off or onto night colours (orange/red rather than blue/green) a couple of hours before you want to sleep.

My personal advice would be to avoid bed altogether - at least if you have somewhere else comfortable where you might drop off (I regularly sleep on my sofa for a few hours). In bed we're thinking 'should be asleep' because that's how we're brought up so another space might be more relaxing.

One thing I've found is that if I worry about sleep (as you're clearly doing and who can blame you?) it's not going to happen. At times when I'm struggling to sleep I let myself off the hook (or let the sleep off the hook). I'll get comfy and say to myself that it's ok if I don't sleep, I'm just resting and I can do that for as long as I like. It takes the pressure off me to drop off. It doesn't always enable me to do so but at least I'm not stressing about it any more.

Good luck, I hope you can find solutions that work for you. You're human. Eventually your brain is going to shut down whether you like it or not because it can't not do. I promise the sleep will come, although I'd suggest not driving or operating heavy machinery until after it has.

One thing sleep people keep saying but it's the opposite for me: Don't read or listen to or watch anything exciting! I guess the idea is that you can't calm down when you do this and that's probably true to an extent but if anxiety keeps you awake (perhaps also if that's caused by your worries about not sleeping) then something that really absorbs you may actually help because it takes the mind off the worries for a bit. It does that for me at least. I can be much calmer after reading a few chapters in a crime novel because I'm not afraid of the crimes commited in Sweden but of far less criminal things in my own life...

One thing sleep people keep saying but it's the opposite for me: Don't read or listen to or watch anything exciting! I guess the idea is that you can't calm down when you do this and that's probably true to an extent but if anxiety keeps you awake (perhaps also if that's caused by your worries about not sleeping) then something that really absorbs you may actually help because it takes the mind off the worries for a bit. It does that for me at least. I can be much calmer after reading a few chapters in a crime novel because I'm not afraid of the crimes commited in Sweden but of far less criminal things in my own life...