>I thnk there are five different cases, nominative, genetive, dative, accusative, and ablative, within a declension. I honestly don't remember there being five declensions.<

There's also a vocative case, although it is only distinguishable from nominative in 2nd declension singular.
I think I learned the 'last' two of the five declensions in about my fourth year of Latin, so it's highly possible you never got to them (I think you said you did two years).

As for the point about Latin teaching grammar and sentence structure, I agree wholeheartedly. My study of Latin is also the only reason I can (or could) struggle through the articles of an Italian or Spanish newspaper and understand at least the subject under discussion even if not the finer points. Great for vocabulary.