Better to take UD classes?

It's hard to answer your question because there are many variables that would go into this decision. I'm sure you are a better student than you were 12 years ago, but does this necessarily mean you should start with upper level courses now that you want to go to medical school?

My opinion, and it is very general, is that you should retake all the pre-req BCPM classes, including the general chemistry courses. I only say this because it has been over a decade since you last took those classes. I think you would be best served on both upper level course work and the MCAT exam if you were to take the time to redo the pre-reqs first.

This may not be what you want to hear. It will add about a year to your timeline for entering med school, but I think that it will be a year that is spent wisely and without waste. The fundamentals are everything. Those must be strong. Even if it doesn't change your overall GPA by much to repeat those courses, it may change your BCPM GPA significantly to do better in them a second time.

Also, consider that for DO schools, if you repeat a class, then the first grade doesn't count toward calculating your GPA..only the repeat grade counts. So, while your AMCAS GPA may not change much, you could likely dramatically raise your AACOMAS GPA. Just something to think about. Good luck.