Applying to medical school does not require any undergraduate major, although you need to take the pre-med courses. However, it does require top end grades, high MCAT scores, and pre-med extracurriculars. Only about half of those who apply to MD schools in the US are admitted by any.
So be sure to make your academic choices so that you will not regret choosing them (from both a personal interest standpoint and a pre-professional standpoint) if you do not get into any medical school.
Regarding math, have you taken an introduction to proofs, discrete math, junior/senior level math course, or honors math course? You may want to wait until you take such a proof-oriented math course before deciding on doing math or not. Note that proofs and logic are also found in philosophy. Ancient mathematicians and philosophers were often the same people.