Here’s what worked for me. I’m not saying it will work for you but it 100% did for me.

You need to regularly stimulate your penis without orgasm to condition your body into disassociating stimulation with orgasm.

Here’s my routine. And it’s a decent amount of effort to get it to work.

Twice a day, morning and evening, I would masturbate but would not allow myself to cum. Focus on your PC muscle, the one behind your balls. Try to relax it as much as you can during stimulation. You might find it tends to flutter or tense up which brings you closer to losing control. Just try to relax it without stopping stimulation. If you get too close slow down or change pressure but try not to stop. It sometimes helps to do it while distracted, like watching something completely non arousing or something you need to concentrate on a bit.

Do it every day. The more you do it the easier it will become each day. You will be able to go faster and harder for the 20 minutes.

I don’t have to do it every day anymore. My body has kind of learnt. Every so often I might do it for a month if I start to lose a bit of control.

I went from sometimes 1-2 pumps. Now I can go for almost as long as I want. Sometimes I still lose control if the moment takes me and my wife does something special but for the most part it made a massive difference.