Coffee, coffee 
Yes, procrastination, self loathing and anxiety.
But they come in this order, so calm yourself by observable evidence that you are making progress.
Like in a game, progress in bursts, from base to base, 'save your progress'.
Make it an habit of 'banking' any advance you make ASAP,
i.e. Make a plan and write / sketch it, Tic
Capture the key ideas about each point of the plan in a few key sentences. Tic
Turn to fist point, expand , express your ideas. Tic
Move to the next point, expand, develop it. Tic
...
Address inconsistencies and gaps. Tic
Add some finishing touches. Tic
You can work iteratively as many suggested. Put a basic version down, then improve it. If you run out of time, you would have a reasonable draft.
To work in bursts, it is good to have some time reminders, waking up alarms as it were.
Fitbit has a programmable regular buzz. My DD was recommended to programme it for every 10 or 5 min, so if she day dreams, she can go back to work. Also helpful in exams.
Remember that you are brilliant, you are a queen of pulling it off at the last minute. You made it to university for good reasons. You did it before, you will do it again.