I know exactly how you feel! I passed my test in feb this year on my 6th test. Mixture of reasons really, very long story, but the end result was that as I failed each test I got worse. Don't know tbh honest as I was ready to pass the 1st test but I should had been able to pass from my 2nd onwards but I ended up in a cycle of failing so I expected to fail, so I failed the next one and so on.
I know what you mean about your legs shaking, I was the same. I would stall when I never normally stalled in lessons because my leg was shaking, I would over steer and clip the kerb etc.
A few suggestions!:
On my 5th test I asked my instructor to sit in the car with me during the test. A lot of people dont seem to realise that it is perfectly ok for them to do that. I found that I was happier having someone I knew in the car as well. They have to sit in the back though, and they cant talk to you during your test. It also meant that when I failed my instructor had seen what I was driving like and had seen what I had failed on, which helped to work on it for my next test. If you drive well normally it might help your instructor to see what you drive like when on a test.
Another point, again people don't always realise that you can ask to take a bit of a breather if you need it. If your legs are shaking etc ask if you can pull up (somewhere suitable though) and have a minute or two break. You obviously cant stop for half an hour but you are better having a minute to calm down than keep driving and panicking.
Don't worry about mistakes you make, they might be less important than you think and only be a minor. I know I was bad with this, I would make a mistake and think I had failed, go to pieces and then realise at the end that I had failed on something totally different. Don't worry when the examiner is writing things down, it doesnt mean it is a fail, it could just be a minor fault, or he could be making notes about the manoeuvres you are doing, the route you are going etc.
I don't know if you will have thought about taking any of the rescue remedy things or not. I know a lot of people who thought they were rubbish and did nothing and others who thought they were great. Personally I found they helped. For my 5th test I had tried to 'Kalms' tablets (which are herbal tablets, boots etc sell them) and didnt find they did much. I spoke to someone though who siad you need to take them longer term. So about 2/3 weeks before my 6th test I started taking the full dose of them ( can't remember the amount, it says it on the bottle) and I did begin to feel a lot more relaxed in general and managed to sleep better as well. I also used the 'rescue remedy' drops/spray on the day of my test which is meant to help with nerves, (again these are herbal and you can get them from boots) you just have a couple of sprays or drops on your tongue. Its up to you if you try anything like this, personally I did feel like they helped but everybody is different. Just a point though, people often take them half heartedly saying they wont work and that they will still be nervous etc and convince themselves they wont work. If you try and think they will they are more likely to, they aren't a miracle cure but are herbs which will calm you down, if you will let them, if that makes sense!
A final thing, I found in the end that rather than going in feeling that I MUST pass, it felt better going in just to give it another shot and to see how it went. If I failed I would just find out what I needed to work on, rather than beating myself up about another failure. Just go and give it your best shot! If you want anymore advice, or just to have a chat about it feel free to PM me if you want. Good Luck!