I'd suggest judging it off how you're going with your recent physics lectures. That's a better indication of where your mind is at than stuff you did further back. Also, what are you doing with the lectures? Just sitting in on them, or are you working problems as well?
I've felt the same thing. Generally did pretty well at physics and maths when I was studying. However, at university I never really "got" thermodynamics. About a year ago I was visiting my parents and picked up one of my Dad's old thermodynamics textbooks and started reading, and found I did "get it" this time, which made working through the problems a little later on much easier. Sometimes it just takes the brain a little while to process stuff and really sort it out, maybe.
And if you do go for test pilot - good luck!!!
