I'm sorry you're scared and freaking out. The best thing to do right now is to go get Plan B, even though it's already been two days. It is still effective up to 120 hours (5 days) after unprotected sex (yes, possibly less effective than if you had taken it right away, but it's still better than nothing, right?). While you're buying Plan B, pick up a pregnancy test and save it for the week you're supposed to get your period. If you're late, take a test. All you can do is wait at this point. Try to calm down!
If you end up pregnant, you know your options. Talk to someone at Planned Parenthood who can either refer you on to an adoption agency or pregnancy counseling and prenatal care, or discuss abortion. There are people out there who can help you!