4 year breakup- HELP

so I’ve been with my boyfriend 4 years, we’re 22 and 24. Let me keep it a long story short, he’s a SEVERE narcissist I can’t even live this life anymore, I want to break up but I feel trapped because of our dog. Yes it’s a dog but I don’t even know how to go about this, he’s the only thing that makes me happy anymore. My excuse of a bf makes everything about him, gaslights me, ignores me, doesn’t have sex. I feel like there’s no way we could share the dog bc he’s a narcissist and needs to be out of my life completely... there no way he would let me keep the dog so I feel STUCK in this relationship.. I hate my life, honestly. Anyone who’s dealt with a narcissist understands truly how bad it is.