I have my test in just over two weeks and I am dreading it.
I learned way back when I was 21 and found every lesson torture. Took my test at 22 and failed on one major with no minors and was so upset that I didn't even consider trying again for years and then I wasn't allowed to for health reasons for a few years. I finally plucked up courage to try again last year and got dh to book me some lessons for my birthday.
I now have the loveliest, most patient female instructor, have had just short of a year's worth of lessons, with a few missed here and there due to health issues and I thought I was doing ok, had got used to my weekly lessons and relaxed a little, then was 'encouraged' to book my test and have been slowly going to pieces ever since.
I am pretty sure my driving is ok and without the nerves I would probably pass the test, but with my anxiety levels already through the roof about it, I can't see it being a pass. I can't take beta-blockers either, so that's not an option for me.
I really want to push my test back, although with the waiting list it won't be until the end of August now if I do that, but everyone is nagging me, saying I won't feel any better about it then and to just go for it and treat it as a practise test if I fail. Unfortunately that's not making me feel any better.
We have a family car that is on the drive all day every day, as dh now cycles to work, but I'm not convinced I will be brave enough to drive it on my own even if I do pass the test.
I totally understand your anxiety op. I have decided all I can to do is grit my teeth and give it a go, then have a think, depending what happens on the day. The pressure from other people to see it through is unbelievable and even though it's really none of their business, I know they're right really. Also, if I did move my test date, I'd never hear the end of it. 
I have a lesson this week, one next week then it's my test the following week. I've asked if I could book some extra lessons, as I think I'd feel better with a few more hours practise, but my instructor says I don't need to, because I am a good driver, the skills are all there and it's just my nerves about the test that are getting in the way. 