In terms of intellectual difficulty, Organic Chemistry >>> Calculus I.
In Calculus I, you can literally just mindlessly memorize a few rules to do differentiation and integration (e.g., memorize power rule, chain rule, etc.)
In Organic Chemistry, you need to memorize a lot (read: at least 10x) more rules (and to do well, likely to have some baseline understanding for why the rules exist).
As a math major, I would STRONGLY recommend against this attitude. Though it worked for the poster and others, memorizing f''(x)g(x)+g'(x)f(x) and thinking you understand calculus is one of the main reasons why our mathlab gets flooded with students at the end of the semester, desperately trying to learn the subject at the last second.
Differential and Integral Calculus, like all computational math, requires constant practice, much like organic chemistry. Furthemore, a successful calculus student will not just mindlessly find a derivative of a function, but will understand the meaning of the step, and its implications. Expect word problems and other questions asking you to demonstrate an understanding deeper than the chain rule.
Like others, I also strongly recommend against taking calculus until you have mastered precalculus. A thorough knowledge of algebra, trigonometry, as well as a certain level of developed mathematical intuition, is suggested. I can't tell you how many students evaluate a triple integral in Calc III and then flub the algebra at the end, or still don't understand trig other than having memorized the unit circle. If you want to make up for the bad grade in precalc, I'd retake the course and ace it, and then move on.
You can do it OP, you are obviously very bright! Many students in the mathlab have had bad experiences with math, and have convinced themselves that they will never understand it. While understandable, it is almost always not true, and with hard work their feelings are eventually reversed. If you retake precalc, I'm positive you will feel that lightbulb finally turn on, and you will understand the material at a deeper level; sometimes it takes a second pass. Good luck!