first of all, I need to ask, is calculus required for your major? If not, I would drop it like a bad habit. Most of the time the first test you take in the class is a good indicator of how well you will continue to do (provided the test was of equal difficulty to future exams). And if you're bombing now (especially in math course) it's probably because you lack foundation in the subject.
If you're only taking calculus because it's a requirement for some schools I would wait until the summer when you can focus solely on the class and probably do better.