What should I do when my boyfriend refuses to stop using cringe nicknames for me because he thinks I secretly like it?

I've made a post about this before lol, where I mentioned that my boyfriend has the nicknames BUBU and DUDU for me and him respectively. Well now that's gotten worse and bubu is now replaced by BUBUGIRL. I'm constantly telling him to stop for the love of God but he doesn't budge because he thinks I secretly like it. I've told him to his face that no, I don't secretly like it, I hate it especially when my friends tease me about it. He thinks I'm lying and that he knows me very well, that's why he doesn't stop. What do I do to convince him I'm not bullshitting him and that I really don't like these cringe nicknames?

What should I do when my boyfriend refuses to stop using cringe nicknames for me because he thinks I secretly like it?
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