Advice !!

So my boyfriend and I have been together for a little over 6 months and are sexually active... Recently, he’s been wanting to try new things like talking dirty and naughtier things, but the one thing he wants is for me to talk about having sex with another guy. It turns him on hearing me talk about it, especially talking about his friends.. Personally, I hate it and I’ve talked with him about how that’s just is weird for me, because I’m not in a relationship with them, but with him and I don’t want to picture myself with any other person emotionally or physically, but he see’s it as naughty and sexy.. How should I go about this? Any suggestions or new ideas?