Hi Ford, I think this problem steems from masturbating and you used to much pressure when you were masturbating, next time your having sex switch to doggy style, two ways get your wife to keep her legs together as this will give more pressure, or taken that you have a foreskin, with two fingers hold your foreskin back exposing the head of your penis, your find that the extra friction that this will cause will help you ejeculate, works for me every time.
Good Luck
Do you have this problem while masturbating, if you do masturbate? If not, then you are probably used to your own self and what you do. Another reason could be hormone related. Hormone levels can start dropping in men as young as their 20's. So, you may want to have your levels checked.