24 is notttt oldddd. A lot of students take a gap year (or two) to beef up their app. My UG school even recommends taking a gap year to ensure your MCAT is good, fix any GPA mishaps, and get some good experience out there. It's hard to determine exactly what you need to do because there's no info on UGPA, sGPA, or any EC's.
You're not crazy. But it is good to be realistic about what you want to do and need to do, and why you want to do it. I feel you when you've known you've wanted to be a doctor since before elementary school, but adcoms have to know /why/ you know that, and what you're going to do to make sure you stay in that. You mentioned changing your major 4 times, that's a little scary because med schools want someone dependable who knows for sure what they want and are going to be a good physician/person who can do a good job in the next 40 years.
Get a good plan going, and maybe talk to a university advisor to help you sort things out. Good luck!