when you find the right guy that you want to give that to, you'll know. for sure. you'll know it will be him, you may not know when but you'll know it's going to be given up to him.
i've been friends with this guy for a year, talked about a relationship for five months, but he just "officially" became my boyfriend four days ago. we haven't had sex yet, but i know that my first time will be with him. i think it's something that happens when you really truly fall in love, you just want to give that person everything.
the only reason we haven't gone that far yet is because i don't think i'm ready for it right now. i think that because i had to question it, i think if you have to ask (like you are) then you're probably not ready.
no matter what you choose though, do what you think is best. and if you need to, talk to him about it. let him know you want him to be your first but you're not sure if you're ready for it yet, you know?
and i say; never let society's moral standards dictate ANYTHING. whether you sleep with him the day you start going out, the next month or in ten years, it doesn't make you a bad person. when the time is right, go for it. and don't worry about anyone else's views on it, because that's all about you and him