So far all my friends this year have had exactly the same feelings as you are describing. There have been a lot of tears in my friendship group, including one who seriously considered cancelling her place to study medicine. However every single one of them that has gone has absolutely loved it once they got there and say how silly they feel for dreading it so much!
I think what you're feeling is completely natural and most likely is just cold feet but once you get there you should settle in very quickly. Also bear in mind most of your fellow students will probably be feeling a similar way to you. If worse comes to worst and you get there and and find that you're really not enjoying your course or university it's a fairly simple procedure of switch courses and/or university or take a gap year.
Also just because you have a law degree you don't have to necessarily become a lawyer, it's such a good degree to have that can open so many different doors.
Please don't worry yourself though what you are feeling is entirely normal and expected but I'm sure that once you are there you will love it. Good luck.