Hi there, I think one consideration may be on your decision to apply to MD or DO schools. Since you have written in the pre-osteopathic forum, my assumption is that you are planning to apply to DO schools (or both MD and DO schools).
Honestly, you and I both know that the chances of you getting into a medical school with a 2.9 is not an option for an MD program, and a very slim chance at a DO school. Maybe those odds would be helped if you are URM, or have a seriously strong upward trend... but otherwise, highly unlikely. (I think I may have seen a few students get accepted to a DO school with a 2.9, but those students are VERY rare, and must have a lot of other things going for them to be accepted with such numbers.)
The nice thing about DO schools is that they take your repeat grade, while MD schools average the two. So if you are interested in DO schools, then retaking those classes in which you received Cs or lower would REALLY help improve your GPA (as those original classes you did poorly in wouldn't factor in your GPA). They'd still be on your transcripts, and the adcom would still likely see your original grades, but you'd get quick GPA inflation for DO schools if you can retake a lot of those classes with poor grades and make sure to get As this time around.
If you feel much more strongly about doing an MD program, I'd suggest going the post-bacc route.
If I were in your situation, what I would do is look at my transcripts, and see which classes I got the poor grades in. If it were limited to 5-6 classes, I'd consider taking an extra semester in school to retake those 5-6 classes and get 'A's in them. If by retaking those classes and getting 'A's, you can bring your GPA up to like a 3.2-3.4 by AACOMAS standards, then I'd say do that.
When you are ready to apply for med school, you can also apply to DO schools and post-baccs at the same time. Then if you get into a DO school, run with it.... otherwise, if not, just enroll in the post-bacc program before applying again the next year.