Without your stats its really hard to comment. If you KNOW you want to be a doctor, don't waste time take the required classes, take them over if you got C's, and make sure the rest of your app (EC's) are good.
You can get into medical school with any major. I just graduated with a BS in public health, and I am applying right now. Just make sure to get all of the requirements in for medical school, and retake classes that you did poorly in.
Pre med requirements are minimal. Biology, Chem, O-Chem, Physics. Can you not add those courses on the side? Also, medical school is something that even when you are in it, you will ask yourself "what have I done?!" Make sure you just weren't enamored with the ceremony and that you are getting into medicine for the right reasons.