Ok don't panic - everyone's done stupid things at some point in their lives so you're not alone!
it could well be that you're stressing over the idea of being pregnant and that is what is making you have 'symptoms'. It's easy to think every little twinge is pregnancy related if it's on your mind. Best thing to do is take a test if your period doesn't come when expected and if it is positive then you will really have to think hard about what you're going to do. None of your options will be an easy one. If it is negative then you really need to get yourself down to your doc's and get some contraception sorted out. Don't just rely on condoms because it is so easy not to bother.
When I was a bit older than you, I had the .Implanon implant in my arm which lasts for 3 years. It worked well for me, although it did give me rather more frequent periods than i'd have liked! I'm just wondering if that or the .Depo .Provera injection might be good ideas for you because you might forget to take the pill.
Anyway, try not to panic right now, just don't have any more unprotected sex and wait until your period is due.
Best of luck!