I am finishing my undergrad and probably half of the Bio B.S. pre-med students I am friends with have changed their major and career goals, with poor grades as a major influence. Most of them have enough credits in psych, comp sci, zoology, etc to pursue those majors because they were interested enough in these subjects to take classes in addition to the Bio major required courses. We all have other passions besides becoming doctors, and I see that my friends are more passionate and optimistic on their new career path. It sounds like you are in the same situation, so don't feel ashamed or defeated that poor grades influenced your decision - it probably will make you happier in the long run. To illustrate this, I was definitely pressured to pursue a career in medicine even though my first two years at uni I was studying to become a wildlife ecologist. I have done really well with grades and the MCAT, though, so I haven't had any reason to reconsider pursuing what I am possibly more passionate about...until I read this post. Anyways, good luck in your new endeavors!