Get yourself some kind of birth control, and ALWAYS make EVERY guy wear a condom, you never know where or who he has been with...don't tell him you use birth control, that's an excuse for him not to use a condom!
You should probably get on some sort of birth control. That's your best option. Also make him use a condom especially if you know he's been with someone else. Just make sure YOUR ready. It's way more to sex then just the physical part. Your tying in so MANY emotions when you decide to give your body away. Coming from my own experience I wish I would've waited.