Some Advices Regarding to Preparation for Mathematics Graduate Programs
Disclaimer: I'm not in the field of mathematics, but I have been in a similar position

I think it is still possible for you to switch to math. It helps to get some more research experience if your GPA is not that great. A good reference and research experience will make up for a lower GPA in a lot of programs. I had some mental health issues during undergrad, and took an RA position for a year before applying. I cited health issues as a reason for my poor grades (&lt; 3.0 GPA), and asked the professor I worked with during undergrad to mention this in his letter of recommendation. I don't think you have to explain your mental health issues in detail during the application process.