did u see ur doc ? if so wat did she or he say?
I find that it helps to think about something else when you're about to come. I didn't say someone else, but something else entirely ;)
Do you use a condom? There are certain types of condoms which are thicker and reduce sensation in the penis, maybe you should give that a try. If it doesn't help, the minute you think you're about to ejaculate think about something that worries you. For me, it's spot-on. I can't ejaculate if something important is on my mind.
Good luck
Many men have the same problem, i hear alot of men saying that when they think there near ejaculation, they slow down to stop it happening...its all about control...just slow down a little, tht should help you last a little longer.