Karly: You got some really great advice and there is no way you can go wrong is you take them to heart. The most important thing to remember is that your body is the temple of the Lord, and in the same manner we treat natural temples with reverence and respect, how much greater we are to treat the temple in which God resides? In 1 Corinthians 6:19, 20 we are reminded: "What? know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own? For ye are bought with a price: therefore glorify God in your body, and in your spirit, which are God's.
Sex outside of marriage grieves the Holy Spirit, and breaks the heart of God. It was not what He intended, and while it may seem your friends are having sex and doing OK. it does not mean that there is nothing wrong with what they are doing.
Do not let the devil mess with your head. While you will not find a verse that says: "Thou shall not have sex outside of marriage", as others have pointed out, it is covered under sexual immorality and fornication. The only winner in this situation, should you and your boyfriend give in, is the enemy. There is no way you can win.
Another thought: if all your friends do is talk about sex, you need to re-evaluate those friendships. Find some friends who can encourage you in the Lord and who can hold you accountable. God has a plan for your life (Jeremiah 29:11) and seeing those plans come to you blessed, doesn't it make sense to seek them out? Yes, it is challenging when harmones come to the fore, but the Holy Spirit of God is more than capable of taking you and your boyfriend beyond your human limitations. Again we are reminded: "There hath no temptation taken you but such as is common to man: but God is faithful, who will not suffer you to be tempted above that ye are able; but will with the temptation also make a way to escape, that ye may be able to bear it." Yeild yourself to the Holy Spirit, spend time in the Word, and allow the Spirit of God to work in your life that you will live same in a manner that brings glory to Him, and much blessings to you. God bless.