As a person with a huge amount of anxiety, I understand you. You aren't alone in this.
You have to have confidence in yourself though, you're ranked highly in a strong cohort, that in itself is a big achievement.
You're struggling to study and that's okay, from what I've done to help with this in the past is change the place that I'm studying in and try to be in a more outdoor environment or somewhere where I can see outside a window- it's very calming. Then I'd recommend that you time yourself for 30 minutes and just try to complete as much revision as you can. Try to create mind maps and see what you're weak in within that 30 minutes. After that, take a break and come back to work on what you couldn't think of many ideas for.
I wish you the best of luck. Remember, life goes on and this is just a small task which won't really matter in a few years time:)