I wish I could leave my boyfriend

I wish I could leave my boyfriend without feeling like I’m getting all my limbs cut off. We’ve been together 9 months, we’re long distance but he comes to stay with me for a few weeks every 2 months.
these last 2 months he’s basically ghosted me to play with this other girl, I’m so miserable bro. I cry everyday, I have anxiety attacks literally daily but it doesn’t compare to the horrible feelings I get when I leave him. He treats me so bad, like insanely bad. So why can’t I just let go? Why am I okay with being treated this way, I’m not but deep down I must be if I stay. I’ve tried to scream, cry, plead, beg, communicate, be calm and talk and all of it gets ignored. Genuinely, ignored for hours and when he does respond he talks about something completely unrelated. I want to leave so bad, I don’t want to love him anymore. I really truly do not want to be in love with him anymore.
He gives me love like feeding a desperate dog. He takes it away whenever he feels like it. He watches the destruction of my mental health and just sits there, he doesn’t do anything but watch. And he’s completely unfazed. I feel like I’m losing my mind, I wake up from nightmares yelling and screaming and I end up puking from it. He gives me anxiety attacks so bad I’m throwing up and I’m so close into relapsing into horrible behaviours and he knows and doesn’t care. I know he doesn’t care, I know he’s okay with treating me like this so why do I stay? Why can I not leave someone I hate being with. Who hurts me so bad