Hi Naj18,
I understand what you are going through. Though you shouldn't be comparing yourself with other students, as often they are going through the same issues. Your supervisor sounds "delightful" but if you say the speed not the workload is hurting you can potentially fix it. I find that deadlines can trigger anxiety and there is a lot of help out there for dealing with pressure anxiety. Otherwise, if your supervisor still focuses on speed you could adopt a "good enough" attitude and learn to be comfortable doing just enough to preserve your sanity. I would also say you could talk with your supervisor but that isn't easy sometimes but more importantly have you talked with anyone in your lab/depart meant about this? As talking with someone you know can present some very easy fixes or other people might have learnt to manage your supervisor.