There can be a lot of pressure to lose your virginity – that is, to have sexual intercourse for the first time. Having sex with someone just because you want to lose your virginity, or because you think all your friends are doing it, is something you may regret later.
You might feel lots of anxieties, especially the first time you have sexual intercourse (often referred to as ‘having sex’). You may feel embarrassed about how you look without your clothes on, or worried about your privacy being disturbed. It’s natural to feel some worries but good communication will really help to prevent you feeling embarrassed or worried. You should be able to talk to your partner about how you feel about having sex for the first time, and about any concerns you may have. Your partner might be worried, too. Being relaxed and able to share things with your partner will really ease the tension. And if you’re too shy, or you’re not able to talk about these things with your partner – then you probably shouldn’t be having sex!
Having sexual intercourse – when a boy’s hard penis goes inside a girl’s vagina, or even just touches the outside of her vagina – is what can lead to pregnancy. So, before having sexual intercourse you should think about whether you need to use contraception to prevent unwanted pregnancy, and condoms to prevent Sexually Transmitted Diseases.
see more in here http://www.avert.org/sexual-intercourse.htm