My ex didn’t know the word

You sure he wasn't a narcissist

Google it

I had a partner who was abusive. He would twist things around to try and convince me I was the one who was abusive. He would try and convince me things hadn't happened. If I brought something up about his behavior towards me he would say I was imagining it, or i was a psycho. If I became suspicious he was cheating or using drugs, he'd say I was paranoid and a stalker. He would tell friends, family, people I worked with, these little stories about me being controlling, a liar, abusive to him, or paranoid, or having psychotic episodes, so when I eventually tried to reach out to someone about the abuse, they thought it was me because he'd gotten in first with his little sly comments over time and really ruined my character without me knowing.
Occasionally I actually thought everything was me overreacting and I was going crazy! I ended up having a breakdown and suffering anxiety and depression because of everything.

My ex never heard of the word

^ My husband would have no clue what gas lighting is. He doesn't hang out on classy forums like this to find out these things. And if I didn't visit this site I'd have no idea about heaps of things that aren't relevant to our relationship. Some terms aren't general knowledge.

God damn there are some bitchy know it all assholes on here tonight

That doesn't sound like gas lighting, just an insensitive partner