I have come across some pre-req problems that I may have..and a bit scared..theres two pre-preq (gen chem II and physics II) that i have a D in (~1.2) Is that going to be a problem for admissions/ or when I come back to the US for residency's? Is there a requirement that all pre-req classes have to be higher than a 2.0?? I have since improved in my gpa and studied my butt of for the mcats to pull a 27. I'm really scared any advice would be appreciated.....

Nobody is going to care that you got D's in gen chem and physics when you apply for residency. However, it is going to be a problem for medical school admissions. You should retake them at a 4-year university.