Think of your virginity as something to give to someone worthy , you don't want your first to be just anyone it should be someone special and your surroundings should be special. You will regret doing Joe Doe in the backseat of his parents car.
Sex is very personal and you should not let what other people are doing make your decision for you. It is your body you will be the one to live with the consequences of your actions. If your friends do not understand why you feel you should wait tell them to butt out your sex life is not their business.
I was a virgin until I was 20 and I can tell you that by the time I got to twenty the majority of my friends had "done it" they mostly wished they would have waited for the right one . While I realize 20 is "old" for losing it I was with the man I love- and we are still together 6 years later.
At the very least I would hope you can wait to find someone worthy of you, someone you will want to share this memory with and take it slow , you will always remember your first time and who you were with make it count.