I've had this happen to me yes, sucks to be us. But I wanted you to know you're not alone.
Luckily for me, I have moved past this stage, so its a non issue these days.
I personally did what was suggested in the first reply to you.
Whenever my bf said something that somehow reminded me of my ex, I would counter that thought with "Rowan is not like him, they're not the same, that was then and this is now, He will never beat me up, he's the good guy, stop getting them confused, don't let the past ruin our present " or similar thoughts.
Basically I just countered each negative I came across with 3 positives and I repeated this pattern until it sunk in.
The other thing I did is this, if it was a specific word, I would look up the definition (to get a clear "clinical" description without the emotional attachment) then ask him why he chose to use it...
Then I would mull that over and see if it applied to me, and try to view it as JUST A WORD, and not an emotionally charged one, created and defined for the soul purpose of hurting my feelings ...
I've actually only once told him "Don't call me that, I hate it" and explained why. He was taken aback, because he was saying it in jest and had no idea.
I eventually managed to get over that one thing though (It was "drama queen" btw lol) and it doesn't bug me at all anymore
I even use it often myself now
I didn't want him to have to alter his vocabulary because of me, because I know he's never said anything malicious. So while back then I was grateful he refrained from using that term, without me even having to ask, I did let him know when I was over it.. Hehe
I'm really sorry you're dealing with this, its so unfair to have our past hurts haunt our present happiness, but it can be overcome.
Therapy is an excellent suggestion to work through these types of things.
I hope you get a handle on this soon