I recommend not having sex with her at this point in your lives. For one thing, your icon shows you are a Christian and I think that most Christians would say pre-marital sex is to be avoided. Also, you're not sure if the consent laws in your area and it could result in your being arrested and convicted. If convicted, you might be subject to things like having to register as a sex offender, meaning when you apply for jobs or buy a house, it'll interfere with your opportunities. Even if there aren't any legal issues, your relationship with her parents, your parents and other people might deteriorate. Her parents might be fine with the two of you dating but uncomfortable or angry about you moving into a physical relationship with their young daughter. You could be looked down upon by others who suspect your motives for dating a younger girl.
Plus, you know, at your ages you're probably not ready to deal with the consequences of sex. At fifteen, she's probably not prepared to make decisions about birth control methods and might feel uncomfortable going to a gynaecologist or clinic for examinations and information. Neither of you probably have money to cover more reliable methods of birth control like Nuva Ring, pills like Yaz or Depo-Provera (it's better to combine methods, like pills and foam and condoms). You may also not have money for necessary emergency measures; I think all sexually active couples who aren't ready for children should have Plan B or know exactly how to get it within 24 hours of sex in cases where the birth control failed or was forgotten. Are you both responsible enough to guarantee you'll use reliable birth control each time, every time, regardless of how passionate or hurried the moment is, or where you are (like in a car or hotel)? She's probably not emotionally ready to deal with a pregnancy scare or an actual pregnancy, which can result even if you use a number of birth control devices.
