Stay longer as undergrad or do post-bacc?

If I were you, I would get rid of that D first!!

 

Personally, I'd just graduate and go back as a post-bacc. I graduated in the spring and I'll be going back next winter (I was on the quarter system) to take a DNA course. I finished all of my pre-med prereq's while in my undergrad studies - but why delay graduation for classes that aren't in your major? Also, post-bacc classes will give you a post-bacc GPA - which is a good thing.

If you weren't a science major, some schools also have a pre-med post-bacc program, which you can finish in about two years (since general chem is a pre-req for organic chem).

Good luck!