I feel for you mate. I had troubles on my AFF stage 4. Instructors kept telling me I just need to 'relax', and it kind of started to stress me out trying to 'relax'.
Then someone gave me this tip and it fixed everything: After you exit and get stable, maintain eye contact with your instructor, check your alti, then give your arms a bit of a wiggle/shake to get the tension out, kind of from the wrist like you are shaking water off your hands. Repeat until you feel comfortable, then worry about passing the level. For me, I had my arms incredibly stiff, and just shaking them out a bit reminded me to relax, then I felt myself just melt into the air and that's when it all clicked and I haven't looked back.
Stay positive, listen to your instructors, and remember the order of importance on any exam-type jump is: 1. Stay safe; 2. Have fun 3. Try and pass.
Good luck.
PS: the fun relaxed jump mentioned above is a great idea to just work on shaking out the tension without the stress of trying to pass.