I think it's a good sign that you can step back (after the moment has passed) and analyze your own reaction to it. You seem to have a pretty good sense of why his words affect you the way they do, even though you don't believe them. I note that you said it made you feel like you were bitchy and unreasonable, not that you are bitchy and unreasonable.
I think it takes a while for our understanding of the "why" of our reactions our intellect (where we understand it) to our emotions (which haven't yet got the memo). It's only been in the last six months that I've stopped having a minor panic attack every time I see a text from my ex, and I haven't lived with him in nearly six years.
Keep thinking and analyzing and talking it over with insightful people like your therapist. It sounds like you are well on your way to greater freedom (in your new vehicle!).