That's fascinating, I never once stuttered during sex. One thing I found a few years back is how much women loved when I'd interact with them saying how amazing they were and really get in their heads during sex. A girl gave me the advice once, that and how nice it is to communicate openly about anything, and a little after when a women came 3 times, I knew it was really nice! Recently we'd both go at it really hard when she's on top of me in particular but I was waaaay too into it...I don't even know how it would be possible? It just didn't matter what I'd say, there was nothing to be beholden to, just what ever comes out in the moment. When I first started having sex and was nervous I didn't really say much of anything. I guess I would recommend taking it slow and just being forgiving in the moment, enjoy every touch and every bit of it without worrying ahead to anything at all. I used to be so nervous having sex with a new person the first time but eventually you trust your body to do it's thing so you may as well enjoy it from start to finish!