Also attempting to finish CS BS but I have hit a wall in my late 30s unable to pass pre-calc. I shudder at the daunting levels of Calc that come after to the point that I'm debating switching majors just to "get a degree".
This may not work for you, but I honestly didn't understand calculus until I worked through Knuth's Concrete Mathematics. There's a portion of it detailing rules on summations, which were (I realized at the time) the discrete equivalent of integration (summation of functions over integers versus integration which is summation of continuous functions). With my (stronger) CS than math background, it just "clicked" for me. You could check out the book from your university's library and see if this material helps you. I can't put my finger on which specifically now (too many years later) but various calculus concepts just fell into place as I worked through those portions of the book.
I feel the same way though, I've been looking back through some basic algebra on Khan Academy too because I feel maths is very much my weak point.