If I were a girl and were you... I'd wait. But if you wanna have sex so much, just use a condom. Even if you haven't had your period yet. You could get AIDS.
No, it is not a good idea. Why would you want to have sex now - because others do or are pressuring you to do so? If you do this for the wrong reason use a condom so you're not doubly sorry - and you certainly will be sorry.
You're really not old enough, but only you can decide. However please keep in mind that even though you haven't had a period you could still get pregnant so you should use protection.
I'm not going to sit and tell you your too young etc. But it is illegal and ilegal for the person you might have sex with becasue you are under 16. However there is no risk you could get pregnant.