You cannot do nursing with a medicine degree.
Medicine, nursing and paramedic are all very different careers. It sounds like the best next step for you would be some good work experience in each of these areas to understand the differences and start to consider which one you might be best suited to.
If you decide that medicine is what you want to do, then the most straightforward way of doing it is by working hard at your A-levels, getting those grades and doing the undergraduate course. Don't aim immediately for graduate entry medicine before you even have any grades.
It is possible to apply for graduate entry medicine with nursing as a first degree, but don't do this if you are sure from the outset that you want to do medicine rather than nursing.
Best wishes.