First of all, unprotected sex isn't a great idea. But if you're pregnant you shouldn't be bleeding like that, maybe you should try a pregnancy test but I really think you should go to the doctor and get checked out anyway... bleeding like that isn't normal.. unless you take the pill and forget to take it for a few days, in that case you would bleed a little bit... but still, go get checked out.
Any time you have unprotected (or even protected) you risk becoming pregnant. The unusual bleeding can be form several things and not just a sign of being pregnant. All you can really do is wait and if your period late, if so take a test with first morning urine.