You can do it, OP, honestly you can. It may be that a different instructor would help, or a different car, but ultimately it now sounds like your nerves are getting the better of you. They can be overcome, because if I can, anyone can.
I passed my test first time at age 21. I have a slight disability which means I'm restricted to automatics only. I was never a confident learner because of the disabilty, and I even doubted that I should have passed the test, that's how low my confidence was.
I drove a few times after I passed, but very infrequently, and I totally think this was the main reason I developed a phobia about driving-lack of frequent practice. Within a few months of passing, I got all sorts of hang-ups about where I 'could' and 'couldn't' drive (wouldn't do big roundabouts, wouldn't drive anywhere I that I'd have to rely on road signs, etc). Eventually I stopped all together. For 20 years!
When my DS was a toddler I got so fed up of being restricted to struggling on public transport with a disability and a pushchair that I decided to get refresher lessons and give it one last go.
Was the best decision of my life.
It wasn't easy, I was like you...sleepless before the lessons, and the first time I sat in the drivers seat I was trembling and sweating with nerves before I even started the car! But I went with a driving school that was known for being good with nervous drivers, and the instructor was great. Very relaxed, calm, didn't make me ever feel that I was ridiculous. Even when I burst into tears at the wheel in the outside lane of a dual carriageway at the 'incredible' speed of 40mph because 'It was all just too much!'
. Seriously, it was mentally draining to start with, but the key, the absolute most important thing was getting out there and doing it frequently. Practice, Practice, practice. Not just once a week, but two or three or four if possible.
A few months on, and I was driving everywhere. Literally, I have been all over Britain, and there's nothing I won't tackle now. Roundabouts, Spaghetti Junction, the M25...I am confident, and (reasonably!) calm, I get in the car without even thinking about it and I actually ENJOY driving.
Years later, I am still amazed that I could have gone from being so scared of it, to this. So yes, you can do it. It may be worth looking around your area for a driving school that specialises in nervous drivers, I know that made the big difference for me. Getting over my fear really is the best thing i've ever done. Good luck!