It can sometimes be tricky without your parents' consent, at age 17. I would look up your nearest Planned Parenthood and see what they say. In the meantime, use condoms with contraceptive foam.
In America, so long as you have insurance, birth control pills are now free. Some states allow minors 12 and up to go to doctors alone. Check your state laws and/or check with your local Planned Parenthood.