It depends on what you consider "fast". You might read this:
Premature Ejaculation
I'm thinking you are just a normal young guy. So, there are a couple things you can try... sometimes masturbation before sex can help. Another option is you DON'T have to stop just because you have reach orgasm. There are other things you can do to bring your partner to orgasm... or keep things interesting until you are ready to go again. (Just remember... if you've reached orgasm... then you need to wash off and change condoms before round two.)
Take care.