Is it a bad idea to do a math major?

Math majors are hired by a wide range of industries. You can google math careers - there is a lot of information online. Whatever direction you go in, I recommend taking some computer science classes.

My daughter, like you, enjoyed calculus. She found her upper level math classes more challenging (as expected - that’s why they are upper level). They were proof heavy and more abstract than calculus. She liked them but it didn’t come as easily.

It sounds like you are off to a good start. Good luck!