The best for anyone who is sexually active, unmarried and not trying for a child, is for the female to be on some form of birth control (the pill, the IUD, or Norplant) AND for the male to use condoms. Not one or the other. The pill, IUD, etc. will prevent pregnancy but not disease. Condoms will help greatly to prevent disease (given that they are used properly) but are not considered 100% for preventing pregnancy. The combination prevents both pregnancy and disease, both of which are very serious and life-altering situations. The pill does not make someone infertile even after long use.
the best contraceptive is abstinence :) teen pregnancy is a tragedy for everyone. it is best to wait till you are older and more mature. imho