If you are ambitious and want to do Calculus justice, try one of the following:
Spivak, Calculus
Apostol, Calculus Vol. 1 & 2
Courant & John, Introduction to Calculus and Analysis Vol. I & II/1, II/2
Be forewarned anyone of them is enough to get you busy for at least a few months. Do not rush.
Do not turn to Stewart or Thomas unless you only care about exam.
Linear Algebra is also a possible choice, and I suggest (in order of difficulty):
Friedberg, Linear Algebra
Axler, Linear Algebra Done Right
Lang, Linear Algebra
Hoffman, Linear Algebra
Halmos, Finite-Dimensional Vector Spaces
Sergei Treil, Linear Algebra Done Wrong
If you want a more computational taste you might turn to Strang or Lay for Matrix Algebra.
But the theory (i.e. Vector Space) is very important in that your next few years will be miserable if you ignore it.
For both Calculus and Linear Algebra you may take advantage of MIT OCW for their video lectures.
Bear in mind courses like 18.01, 18.02, 18.03, 18.06 (which have a lot of materials available) are intended for all majors,
as opposed to those favourable to math majors (18.014, 18.024, 18.034, 18.700).
All of the above can make you better in
writing proofs.
Another very approachable choice is Number Theory, if you like it.
Davenport, The Higher Arithmetic
Silverman, A Friendly Introduction to Number Theory
Goldman, The Queen of Mathematics
Ireland, A Classical Introduction to Modern Number Theory
Hardy, An Introduction to the Theory of Numbers
You may also step back to AoPS and start all over from Prealgebra to have a more solid background.
For a general picture of math major:
Lang, Basic Mathematics
Liebeck, A Concise Introduction to Pure Mathematics
Hardy, A Course of Pure Mathematics
Aleksandrov, Mathematics: Its Content, Methods and Meaning
For more:
http://www.maths.cam.ac.uk/undergrad/course
https://www.ocf.berkeley.edu/~abhishek/chicmath.htm
http://kiro.fraxy.net/books.php
http://www.cargalmathbooks.com/
http://www2.kenyon.edu/Depts/Math/schumacherc/public_html/Professional/CUPM/2015Guide/CUPMDraft.html
http://maths.mq.edu.au/~chris/notes/index.html