I did computer science and math double degree. I like the computer science but I now wish I hadn't gotten the math and had gotten a second degree in business focus on entrepreneurship. Of course back then I had no idea I loved business so.
So anyway I'd suggest probably business is a good thing to study and computer science is fun if you enjoy that sort of stuff.
Aww as someone that also has a BS in math it's sad to hear you say that.
You would have learned nothing useful in a business degree, just how everyone else does business for the most part which IMHO just ham strings creativity if you aren't going to be an office drone.
A math degree isn't about learning math you will never use. It's about learning to approach and solve problems correctly and creatively, tying up all lose ends into a neat little proof.
Just the concept of being able to approach a problem and thinking "How can I completely prove this is true?" and then doing it is a realm of thinking far beyond anything most people can ever do.