Senior Year Anxiety

I am a senior in high school this year (graduating class of 2015), and I am mostly an above average student, receiving GPA’s between 3.1-3.84 during my high school career. I have applied to my number 1 choice college, San Diego State University, and will hear back from them by mid-march. However, I am severely frightened because I have received 2 C’s on my senior year semester 1 report card (my high school has 2 semesters per school year). I was told that if you receive lower than a B your senior year, colleges will most likely withdrawal your admission (assuming you get accepted). I am terrified at the moment. Is that true? How much did my chances at acceptance go down?