It's okay to vent. You don't need to give up the dream yet, is there a way you take an intensive Chemistry session over winter break to give yourself a better understanding? Does your college have any tutoring/mentoring programs that could help motivate you and get better study habits? They have every reason to want you to succeed, see what you can find out. If you don't already have an advisor, ask in the admissions department, and they will know what to do to hook you up. You already have the love for animals and the desire, now you just need a boost in the studying/motivation area.