Hey I want to be a doctor too and I’m not sure what I’m going to major in either.
I think, in my personal opinion, that is kind of risky considering you just developed the interest in sketching and drawing. (I’m assuming you have no experience whatsoever) However, this does not mean you cannot learn. If I were you, I would minor in something drawing related instead of majoring in it. Also I think we don’t have to declare our majors until the end of sophomore year, someone correct me if I’m wrong, so you could always take a couple courses first and then decide how much you like it and how good you are at it.