how do i convince my boyfriend we're not going to have sex?

[hay_mic2000]

ok so we're both christians and i am FIRM on saving myself til marriage. he's to that horny stage cuz he's almost 18 and always asks if we can and when i say no hes always like "why" and i always tell him 1. its not what God wants. 2. im not getting pregnant. 3. what if we dont get married? im only having sex with one person. and he still asks...so i dont know what to do. any advice??