@Flappy well tbh it depends on which s** scene you're talking about but in general saying " No " in the middle of the play or s** , etc ... is a form of showing their shyness ( NOT ALL THE TIME THO , READ THE ATMOSPHERE PLS ) or it can even be like a reflex of feeling sth new done to them ( ppl are scared of all forms of unknowable things , specially not knowing what's happening when it comes to their body is natural that's why you should be careful with choosing your partner ^^ ) and that's it :))