This used to be a problem for me. Here's what worked to help me gain control. Masturbate until you feel like you're about to cum, then stop. Keep taking yourself to the edge, then stopping. Do this for a really long time, and then allow yourself to cum. It will feel 10 times better and you'll shoot a larger load. Keep practicing this technique. You'll have lots of fun trying
Eventually, over time, you will have conditioned yourself to know when to slow down or stop during sex to hold off on cumming until you and your partner are ready.
My wife and I often switch positions when I'm getting close. This gives you a chance to take a "breather" and keeps things exciting and interesting.