The issue is here: "I have no problem solving most of algebra or calculus problems, but if you asked me to explain what I'm doing I wouldn't be able to tell you, at least not using mathematical constructs/words." This is slightly unclear; there are two possible problems here from what I can see, and they're totally different problems to have. Either you cannot do maths, and you're only good at solving repetitive prob…
The problems in Spivak are pretty good I think - they'll show if you can do maths or not. Some also have answers (and an answer book for the rest), so there's examples of explaining what was done, for harder ones. The explanations are sometimes too concise, but at least it gives some guide for how you can explain your answers. At a much easier level, Khan Academy videos mostly are explaining how a specific problem wa…
When I took calculus there were three things that really helped me with this:
1) A study partner that's competitive. when you have an intuition you're more likely to get the correct answer first because you can check what's going on quickly without having to recalculate things. Also when they get stuck you'll be expected to explain how you figured it out. Studying with someone like this will force you to grow an intuition.
2) Writing programs that use what you've learned. At least for me this helped a lot. I learned to program before I learned any interesting math so being able to rewrite what are often implicit ideas in an explicit language can really help you think things through. Like many people here I gained an intuition for integration early on by writing physics engines for games.
3) Just meditate on the ideas.