Masturbation will not cause premature ejaculation, but instead it will cause POST-mature ejaculation. This is because your hand strength is higher and thus cause more "tight" than a girl's vagina. So in long run your didi will feel numb and the consequence you suffer is you hardly ejaculate.

I assume you masturbate with your hand and after 1 minute you shoot out right? Try stop for 1 month and everything will be normal.

Also, dont be so kancheong when you "do"... take your sweet time.