If you had unprotected sex you could be pregnant. Basic sex ed! Take a test
If your super concerned take a HPT. If it.comes up positive go see a doctor as soon as u can, but let them know you have been spotting. If its negative, wait until u miss your monthly and re-test. Its touchy because I have had ectopic pregnancies and miscarriages very.early on. You could also be having what they call implantation bleeding
Look it up, see what it's About so u may have a better idea.