You just need more sex. Amazingly enough, the more you have, the better your 'control'.

try masturbating before hand or ejaculate during foreplay and eat her or find continue to play till you get hard again to last a lil longer, there are also many posts with tips on how to last longer here, have a search up for them with keywords of "premature"

you may have a case of premature ejaculation or you just might be very aroused at that time..

Search for 'P/e' 'premature ejaculation' and look for dancingdoc's posts. they are very descriptive and are what you are looking for.

Also search 'squeeze technique'