You should check into getting a pregnancy test and getting birth control if your going to be having unprotected test. And the blood is spotting you could very well be pregnant. Get a test .
When I fell pregnant with my first daughter I had light spotting around the time my period was due for the first 2 months, and I was indeed pregnant! You need to take a test to find out. Bringing a child into the world is a very big responsibility and not an easy job. You're only 17, you should be having fun going out with your friends- making the most of being a teenager! You can't get those years back. Like penswriter said, if you are not pregnant you should go on birth control.
If you're having unprotected sex yes you can be pregnant. The only way you'll know is to take an hpt. If you're not pregnant I highly suggest getting on some form of b/c and ALWAYS using condoms.