How can I actually make myself stick to my self-determined deadlines as someone with ADHD? Gentle and constructive advice really needed

So I'm a third year history student and I have 37 days left. I'm going into the resit period with a 4000 word essay, 7 day 'exam' and my dissertation to finish. I know I shouldn't have left so much for resit but my mental health has been appalling this year and my dissertation is really important because I plan to use my niche for further opportunities.

Essentially, I've found myself in a shit position. My dissertation is by no means unwritten- in fact it's way over word count. But it's not structured properly at all, and one chapter has little actual writing. So it's a mess and I need the bulk of these remaining days to make it into a cohesive, strong piece of work.

I decided I was gonna give myself five days to write the 4k essay, starting today. It's not due until the 20th of July but I need it done and dusted so I can worry about more pressing things. In theory, this should be fine. I know the subject extremely well, have lots of research done, a plan and even some very rough draft arguments written. But I find myself completely paralysed right now. When I've had five days 'exams', I have no trouble doing all the research and writing to a high standard and submitting on time.

When I try to give myself deadlines, my brain knows that I have way more actual time and I can't get into action so quickly. Does anyone else struggle with this? How can I trick my brain into thinking I actually only have five days? I KNOW I can produce high quality work in this time but it only seems to work with a hard, non-negoitable deadline.

I'm also an extremely messy writer and planner. I overwrite terrible, I have random passages strewn about everywhere. Even with medication, I'm a mess. I'm moving into a new flat and have had nothing but grief from the landlord so I feel like I'm at breaking point in general and I can't sleep properly. I got maybe 4.5 hours last night and I'm averaging 5 hours at the moment. I'm not the type who can work well on little sleep- 8 hours is my minimum.

I'm just so overwhelmed. I have panic disorder and where I used to have panic attacks and fear death, I now get them and think 'I hope this does kill me.' It seems that I've become WORSE and slower as time goes on. My grades are better but the pressure is mounting so badly that I get less done in a day.

Anyone else out there in my position? And does anyone know any tricks specifically for ADHD brains or for following deadlines you've set yourself instead of university deadlines?

I'm a top student. I cry when I receive a great mark. This means everything to me and I'm crumbling. I can't fail but I also can't seem to get much done and the days are ticking on.