What do I do if he ignores the “safe word”?

My boyfriend and I like to have rough sex but some times it starts to hurt, so I decided that we should have a safe word. We are both WELL AWARE of what the word is, and yet.. my boyfriend ignores it. I keep telling him it’s in place for a reason but he always says it feels too good or “you say it when I’m about to cum” 🤦🏾‍♀️ it’s annoying