I think it would help me to know what on earth is going on to stop me thinking it’s me
How old are you? What is your relationship history?
The fact you think "it could be you" suggests there is an unhealthy dynamic going on. A good relationship shouldn't make you question yourself. Did you question yourself in other relationships or with family and friends?
How I figured it out - I read books, I remember posting on MN, similar to your post. I started to assert my boundaries and tracked incidents. His reaction to my boundaries did 2 things...showed me it wasn't ASD and he was in control of his responses. He changed if others were around. I started to take notice of our interactions, rather than accept them...observe not absorb.
Ex H had a very troubled childhood, albeit middle class, and this was at the root of his interactions. He didn't know what healthy was, it was always about control. In the car example this could be him retaining control. He decides when and if a car is looked at. Your anxiety or concern isn't as important as his need to always in be in the driving seat.
Start believing it isn't you. If that's the case, what can you do next?
Btw, when I asked to separate the extent of his toxicity was revealed as he became very vindictive.