You have lot's of time. Upper level sciences are a little easier than pre-reqs in my opinion, since the grading and curves aren't as harsh. Just do well in the rest of your classes and kill the MCAT. The MCAT should be a good indicator of your success in med school. From what little experience I have on SDN, I think the most important part of becoming a doctor is doing well in "medical school", not "getting into medical school". So, all those people who cut corners and stuff are doing themselves a disservice. Think about post-baccs after junior year if your grades are still bad.