First, don't do four A levels, Doing so gains you no advantage and may may impact adversely on your grades. The exception here is Further Maths with Maths if you are applying to study a STEM subject at university.
Secondly, medicine is a vocation. If you don't have the vocation, don't consider medicine.
Thirdly, in any career you will be happier if you do something which you like doing, not just a thing which you expect to pay well.
There are no subject requirements for a law degree. Also, you can do a non-law degree and then train to be a lawyer by taking a one year course after your degree, followed by a professional qualification.