If you've had unprotecetd sex, then yes, there is a chance.....Take a HPT.
The spotting could be implantation bleeding. Take a test as it would show + or - now.
I believe you could be. My last period (before I found out I was pregnant) was only light spotting for 2 days, and my breasts where swollen and sore. You definetly need to take a pregnancy test. Let us know what happens.......