I have the same problem, although I have it with more than just maths. I struggle with the differences between nouns, verbs, adjectives etc, and the annoying thing is, I KNOW the information, I just don't remember it correctly - I didn't grasp it immediately, my teachers did not help with that, and thus it's almost habit for me now to assume I DON'T know, even when I do.

Being one of the smartest kids at my school (which REALLY is not saying much XD) meant that I was expected to just absorb information and understand it instantly by the majority of my teachers. Nine times out of ten, they took out their frustration at my need for different explanations to the rest of the class by pushing me to one side - I can only ever remember one teacher responding to my 'I don't get it' by sitting down with me and asking what, and why, and helping me to figure it out myself. And I can still remember the huge smile on her face when I DID get it.

Best of luck with retraining yourself - I might follow your example and give it a go when I have spare time (so when I retire XD)