At what point does it become rape

I was thinking about this today, at what point can consensual sex become rape? Is that a thing? Let's say you're having sex with your boyfriend, it's all consensual but then it starts to hurt and you say stop and he doesn't stop and continues to hurt you, is that considered rape? This has happened to me more than once with more than one guy. Whether it be because of pain or just because I was done. I don't consider myself raped but I do consider it.. Just not okay like if i say stop you fucking stop. I've even had a guy hold me tf down and cum inside of me after I told him not to and then he just acted like nothing happened. (I was on birth control and that's one of the reasons I dumped him)