retaking the grades below a C should replace them with your new grades. See http://admission.universityofcalifornia.edu/counselors/q-and-a/repeating/index.html
Rather than spending time worrying about dream schools you should instead figure out why you are doing poorly and what you need to do to fix it. Your CC should have a study skills center. Many students, it turns out, have never learned to study effectively. I recommend reading the book “Make it Stick” this summer; it explains what is known about learning and how HS/college students can apply it.