For what it's worth I felt very similar to you when I was learning. I couldn't get the hang of it at all, everything felt overwhelming, I felt rigid when driving and never really in control.
I used to come into the house and scream at my dad that i'd had enough and I was quitting. And he's always talk me out of it and i'd go again.
There was a moment though (which I can still vividly recall) where it felt a bit like a fog clearing, and suddenly it dawned on me that I was in control of that car, and I stopped concentrating so very hard on every little thing, and began to relax and look ahead on the road, start spotting hazards up ahead and anticipating things, rather than letting everything come as a surprise and create tension and nerves. From then on it was a whole lot easier. Well, I mean, I still failed the practical twice (and my instructor refused to speak to me all the way home after number two), but I got there in the end. It was far from plain sailing though.
I guess my advice is to keep at it, and try to relax and start taking note of your surroundings, as well as the specific controls of the car itself. That was the big thing for me. Once I realised I could control the car, and began to look towards everything that surrounds it - that's when I really started to learn to drive.