You have two courses of action, you can tell him straight up you don’t like what he does during sex. You don’t find it stimulating. You need him to slow down. That may get a negative reaction from him. You could try the other more effective way of really giving a positive reaction to things that you like. If he is slow for just a moment moan and tell him that’s how you like it!… most men will repeat things they got a big reaction for. You can also take some charge over him, I know this is not him being dominating but if he needs to be taught you need to teach him, so use your hands and body to regulate his speed and thrust, help him learn to be slower and more gentle, tell him to touch you more softly, guide his hands. Once he understands what you want than you can set him loose have him hold you down and take the wheel of your sexual encounters!