Does abuse always continue

Me and my boyfriend of 4 years have always brought out the worst in each other. Though in between , we do have good fun times. He’s always been a little aggressive. Like when we tried anal sex and he wanted me doggy style, he pushed me aggressively on my back when I moved out of discomfort. Recently (twice) he’s slapped me hard during sex. Not a sexy , rough -play slap. But slapping me hard while I’m crying and asking him to stop. Even before, when he did it lightly it just didn’t turn me on and I’d cry a little because it’s a slap to the face soft or not. But this last two times were different. And I’m also noticing he doesn’t respect my boundaries. Like with the soft slapping. If I don’t like it then why keep doing. I’m obviously uncomfortable. But it’s been 4 years. And I don’t feel like he’d hurt me badly like punching or dragging me. But I don’t want my boundaries crossed and ignored on a regular basis. And now that he has slapped me that way, I don’t know if it will continue. Has anyone stayed and the person mellowed out? He’s never done that until recently so in three years he didn’t do that. Slapping hard. I just feel very confused. I feel like I want to walk away but I don’t want to hurt his feelings. For some reason the thought of hurting his feelings bothers me