It’s really the course load, and not you. Calculus and Chemistry are college weed out classes for potential Engineering and Pre-med students, so they are extremely difficult. You should do like you’ve planned to drop the Chemistry, but try to keep up the Calculus. Get help from TA, tutoring center, or study group to get better for the Calculus. Get yourself a bit more free time to enjoy the college life and talk to family members until you feel better. Decide what to do during the winter break but not now. Daughter took both AP Calculus and AP Chemistry the semester in HS, and she repeated saying that was the dumpest choice she took.