My (21f) boyfriend (23m) wants me to rehome my dog

For background, just over a year ago my boyfriend's dog passed away. I had been looking into getting a puppy for months, but decided to put a hold on it to respect his grieving time. Despite being long distance, I didn't want him to see me with a new puppy while he was struggling with a loss. Fast forward a month and I stumbled across a puppy fair being hosted by a local animal shelter. I fell in love and took her home (at my mother's insistence, knowing how badly I've missed having a dog since losing my own to cancer) and immediately felt remorse. I told him, which caused a fight because I went back on what I'd said to him about waiting. I can't excuse my decision, because it was a split second decision and I was thinking of myself, and I won't try to justify that. He was upset with me for a very long time.

Fast forward a year and all seems to be forgiven and he's even thinking of getting his own puppy. Except today he texts me during work to tell me he still resents me for getting a puppy, he hates my dog, and he refuses to online with her. My dog brings me lots of comfort, I have c-ptsd and having her near me helps me feel more secure. I've bonded with her very deeply but he's given me an ultimatum. Him or my dog. We both agreed to talk to our therapists but he said he doesn't plan on changing his mind and I have no place being upset with him.

I'm heartbroken, I don't want to choose one or the other. I know how I went about getting my dogwas a thoughtless mistake but I'd be crushed and resentful to have to rehome her. Is this just the cost of my actions? Is he being unfair? I’ve asked him what I can do to fix it and all he says is “what you should have done in the first place” ie, rehome her. Please help, I could use some perspective ):