Undergraduate psychology isn't really about mental health as much as it is about science; how sight works (or doesn't :-) chemistry; dogs, rats, sharks, and pigeons; experiments/statistics, etc. One of my best friends at the time was going to be a clinical psychologist but changed her major to social work instead because of all the science, it wasn't her thing. She became a psychiatric social worker for her State instead of a psychologist.

I would certainly take several psychology courses (start with it as your minor?) and see if that was what I wanted. I would also make sure I took some upper class English courses before I switched so I didn't miss out on anything; the first 4-5 semesters of college were pretty "boring" and generic for me; it took until my junior year before I knew what I thought I really wanted at that time.