It's horrid, I am sorry. Remember it might be that the source of the panic is partly that you feel you must sleep, and that because you aren't asleep everything will go wrong. It won't. You won't die, sleep will just come over you when it really needs to, and you don't need to do anything about that. When it comes to lesser inconveniences they don't matter. It is annoying to have to cancel everything because you're so sleep deprived you can't function, but it isn't worth having a panic attack. If you end up that tired, well, you'll cope. It will pass. It won't be as bad as this pressure now.
Do you think you could try the things I said, not trying to sleep...when I said I was up for four nights it wasn't with those things, I was actually trying to sleep.
Mumsnet is here all night so they'll be someone you can talk to if you panic. Make a plan that if you start to feel very stressed you'll post on here, you'll get up and make some tea, etc..
Try not to set yourself up to fail by thinking you must be asleep. If you stay awake it will be a temporary thing, it won't have any disastrous consequences so long as you take care of yourself by just resting and not trying to do normal things while sleep deprived. It is ok to go to bed and think - right, sleep's not working for me right now so I'll just lie and rest my body while watching this etc...
I think you will fall asleep that way, but the trick is not to focus on that as the goal, to really convince yourself that you are ok staying awake and that you expect to be awake watching something. Ideally something not completely gripping but enough to hold your interest and stop your mind racing to other things.
The goal isn't sleep, it is relaxation. You can't make yourself sleep, sleep will occur when you are relaxed. Now you can't relax while thinking that everything is going to go wrong because you haven't slept. So let that go. Clear your diary. Your only plan is to 'relax'. If it seems not to work, just tell yourself that is ok, you obviously need a bit more time to wind down, just keep going with whatever you're occupying your mind with.