What should I major in? It's one of those personal questions like, "Which person should I date?" that no one can answer for you. Sure, others can give you advice. "Your boyfriend's breath smells like cheese" or "That person is a total jerk." But in the end, it's your decision to make. What you major in is how you spend a significant chunk of your college life, so it's important to your happiness to (try to) get this question right.
The good news: it doesn't matter what you major in for getting into medical school.
"But I thought I had to major in biology to go to medical school." Nope. Not only do you not have to major in biology, but there are many drawbacks to being a biology major.
Let's compare biology with an easy major, say history.
Okay, but biology majors must do better on the MCAT right? Wrong. History majors routinely beat biology majors. Why? History majors are substantially better at the verbal section that tests how well you read (and starting in 2015, the MCAT will have a verbal section AND a psychology/sociology section, so this discrepancy in overall score is likely to increase).
Fine. At least biology majors do better on the biological sciences section, right? Wrong again. History majors beat biology majors at their own game, earning an average of 10.0 points on the section to only 9.9 for bio majors. Even the science portions of the MCAT are passage-based (approximately 85% of the questions are accompanied by a passage with information crucial to answering the questions), so good readers (e.g. history majors) are more likely to succeed.
Look, I'm not saying you should switch your major to history. The whole point of this conversation is to show you that you can major in almost anything and go to med school.
And remember, you don't have to nail this choice from the start. PLENTY of students switch majors (80% of all college students, according to some estimates), so if you start down one path and decide you don't like it, you're not stuck with it. Just give it your best educated guess about what you'd like to study, and go for it!