Before you answer this question, here are some questions to consider.
What is your science GPA looking like right now? A B+ is not ideal for O-chem, but what does the rest of your science classes look like?
What is your current standing in the class? Have you had any lecture exams or quizzes yet, and what were your scores?
How many hours a week do you have to commit to studying for the class, and is additional help (tutoring, office hours, etc) available?
What about O-chem is causing you to struggle?
What is your baseline knowledge from O-chem 1? Or, how well do you know the basic concepts from O-chem 1?
Dropping a class is not ideal, although I personally did it ONCE to avoid a B. If you retake it though, you need to get at least an A to make up for the W on your transcript.