I really don't see how (pregnancy aside, that might just be hormones).
The ick killed my relationship with DD's father. We actually had a very amicable break-up and remain friends. I genuinely like him, he's a decent bloke, a decent dad and he's objectively speaking actually physically attractive.
But thanks to this whole lockdown and sharing responsibility for a child situation, we've been speaking a lot more often than we normally do. And it rears its ugly head even now. I've noticed it's ironically actually triggered when he says something nice or expresses worry about me. Anything that a spouse or partner might say sets it off. It's so visceral it actually makes me want to get off the phone with him as it feels as though even the sound of his voice in my ear is too much.
I'm perfectly fine when we speak about our daughter, music we like, work stuff, which shares to purchase or sell or whether getting a white car boils down to a long-term friendship with the carwash attendant.
It's been 3.5 years since we split up. He's married. Doesn't help. The ick overpowers it all.
Don't see how any relationship can survive this if even exes are not immune. Heavy duty brainwashing aside, maybe, but that's just horrific as a thought!