Pre-med and pre-dental are not majors but advisory programs designed to aid those at UIUC who have a desire to pursue medical or dental school after college. Regardless of major, any UIUC student can sign up for the pre-med or pre-dental advisory program. Getting into med or dental school depends on college grades and the completion of certain coures in college, a number of which are science classes. Many with plans to attend med or dental school pursue a science major, often either biology or chemistry, but you can pursue many majors and still get into med or dental school with completion of required courses, high college grades and high test results (MCAT or DAT).
Thus, in applying to UIUC for a major, you can choose whatever major you want, although the more the major relates to science, the more chance that many of the required courses for admission to med or dental school will be part of the same courses you normally take for the major.
As to your chances for admission, all that can be said is that you currently appear to be doing fine to have a real chance of admission but you still have a semester to complete and an SAT or ACT test before one can even begin to guess at your real chances of admission.