Tell him you are too young, you are not ready and it is against the law you are still a minor. If he doesn't accept this then get rid of him - you are worth more than this and should make sure the first time is special and you do it because you want to not because you are pressurised into it. There is plently of time ahead of you, what's the rush. Have respect for yourself and your body and the boys who are worth it will respect you too. Hope this doesn't sound too harsh, but I have a daughter of your age and this is exactly what I would tell her, do you have an older sister maybe to talk to or otherwise I know it's embarassing, but please talk to your mum. If after all has been said and you still go ahead with it, please be sensible and take precautions