I’m glad you sorted out the Chemistry but you need to seriously work on the calculus. Calculus is a subject that keeps building on earlier knowledge – so if you don’t understand the material now it will be hard to do well as the class moves forward. Do whatever you have to do to understand what went wrong in the midterm-- be sure you understand the past material as well as what is being covered currently – see the professor during office hours, take advantage of any tutoring etc.
On a positive, you seem to be handling things in a much more mature, adult, calm manner and you should feel proud of your personal growth.