OP I would start volunteering in a hospital. You can then atleast see, somewhat, if the medical field interests you. There is no reason to go through undergrad with intentions to go to medical school just to find out that you absolutely hate medicine in your junior year. You can also accomplish this by shadowing which will get you better day-to-day clinical exposure than volunteering which is incredibly variable.
Medical mission trips are nice things to do, but they are EXPENSIVE. Look into your University's community involvement office for both medical (if applicable) and civil volunteer opportunities. Instead of paying a huge sum of money (especially if you don't have it), you might realize that your university offers an alternative spring break trip. I never had to pay to go on mine, but this year extensive fundraising is going on for the students to make it happen. Yeah, you're giving up your spring break, but having done it for 3 years it was still fun and worth it. I'm backing out this year though to go to Mexico, hah.
Good luck and don't oversaturate yourself yet with ECs.
OK; I'm only going on personal experience. I almost definitely went over-the-top with my last post. Obviously, I'd suggest more than a semester. That said, I'm a huge fan of research as an EC.
