Calculus and analysis is commonly the entry point to "serious" mathematics for engineers and physicists but it is certainly not the "only true way". It's not even particularly the usual way.

I recommend the content covered in MIT 6042J, Mathematics for Computer Science (https://ocw.mit.edu/courses/6-042j-mathematics-for-computer-...). The most important part of this course is logic and proof-writing, both of which are foundational tools of serious mathematics, that sometimes get elided if you come in through the physics side (i.e. via calculus and analysis). You will also learn discrete mathematics, i.e. "a bunch of stuff that is useful for cryptography". But I think the foundational stuff about logic and proofs is even more useful. It will rewire your brain in a way that prepares you to go deeper in maths.