crappy semester

Hello all. I’m a little concerned about my chances of being accepted into med-school. I am currently a sophomore and this semester turned out to be my worst. After my finals, I expect my gpa to have dropped down to around a 2.5 this semester. Currently, my overall gpa is 3.77. I believe there are two reasons for this: For one, I believe i took on too much this semester. I volunteer 4hrs. a week in the ER at a local hospital, I have to work at least 15 hrs. a week, on top of that, had 17 credit hrs. of school Chem101, Bio200, psych324, and calc. 121. The second reason is that it is taking me some time to adjust to course work of a large university being that I came from a small community college. I will probably walk away from chem101 and Bio 200 with a B- or C. Even though i still have some time to get my gpa up, should i retake these courses as well to raise my gpa? Will med-schools average in the old grades even if i retook these courses and got an A? How much will this semester have an effect on my chances of becoming a doctor?