light brown/red blood a week after period...pregnant?

So, i had unprotected sex last saturday night/sunday morning (12.30am ish) he pulled out and said he didn get any inside me but i am not sure and half an hour later realised i had started my period....i took the morning after pill on monday 12.30pm lunch time.... My period (anything from 3-5 days) only lasted until monday night, on tuesday morning there was nothing from the night before. Normally it trails off but this just stopped dead. Today is a week later and after going to the loo, i wiped and then saw dark brown/light red blood on the paper, not a lot but noticeable. It is too soon to take a Pregnancy test but i'm hoping somebody can help out. I also have been taking tablets for bowel spasms for two days and don't know if this makes a difference? I have light cramping too. Thankyou!!!!