Bro, if the person is already fucking you then he/she likes you (i hope). That should literally be the last thing on your mind when your having sex. Let go, enjoy it, and for God's sake don't be worried about your speech during one of the most beautiful things in the world. I stutter and not a single girl ever has done anything other than be into it when i talk to them during sex. 99% of the shit you worry about never happens. Be free my man!