I've posted this before so have copied below:
You can train yourself to last longer, I did this when I was younger and have always been able to last a long time and control when I cum. Practice kegels (squeezing the muscle that stops you peeing mid flow) 100 quick reps a day followed by a 10 second squeeze/hold. Then when you wank don't allow yourself to cum, as you feel yourself approaching orgasm stop and squeeze the kegel muscles until the feeling goes. Then continue with wank, repeat process 2-3 times and crucially don't allow yourself to cum on the last one, difficult lol. Practice regularly and only allow yourself to cum once a month or at most once a fortnight (serious willpower required!), I used to do it for an hour at a time pretty much every other day so its a serious time commitment haha. I was doing it during my single phase so plenty of time to practice but once I was with a girl I had no problems at all lasting. The long sessions train you not to get overstimulated and finish early and crucially teach your body to recognise and control when you're going to cum, rather than trying to think of something to distract you and then you suddenly can't stop you feel the early stages, slow down or change position and pace yourself. Once you get used to it you won't need to keep up with the 'training' quite so much and can cum whenever you want (otherwise you'd go mad lol). Worked for me.