You should definitely not give up, yes Stony Brook is an extremely competitive program but the good thing about Stony Brook is that they do not look at grades alone - they look at a mix of GPA, reference letters,essay, pre-requisite grades, volunteer experience etc. Because you do not have all your pre-reqs done and are currently retaking some because of poor grades you may have a harder time getting in. I suggest doing what you can though, retake them, if you don't get in reapply next year! Always have a backup from another school because there are very limited slots. Good luck, don't be discouraged by others.