I had this problem in my early 20s. Google the "stop start technique". You train yourself during masturbation and once you are fully trained you will be able to last as long as you want when you are having sex.
The technique involves this: There is a moment during sex when you are building up to a climax. Learn how to recognize when this is happening. When you identify this happening you slow down or even stop briefly if you have to and then the buildup stops and reverses. Then you can keep on going. After you do this a few times during sex it will be harder to cum.
The buildup is worst during the first couple of minutes but once you make it past the first few minutes it will be very easy to control ejaculation. If you do this technique too many times during sex the biggest problem is that when you are actually ready to cum, you might not be able to.
The technique involves this: There is a moment during sex when you are building up to a climax. Learn how to recognize when this is happening. When you identify this happening you slow down or even stop briefly if you have to and then the buildup stops and reverses. Then you can keep on going. After you do this a few times during sex it will be harder to cum.
The buildup is worst during the first couple of minutes but once you make it past the first few minutes it will be very easy to control ejaculation. If you do this technique too many times during sex the biggest problem is that when you are actually ready to cum, you might not be able to.