Don't know what to expect.

I had sex on July 23rd, the day after the most fertile date. 9 days later I saw a very very small amount of pink blood. The next day I checked my pad (i thought I started my period) and I found the same amount of brownish blood. I waited a day and I didn't see anything else. The same day I was spottin, I was having abdominal pain but it wasn't too severe. Could I be pregnant? AF is suppose to appear tomorrow but my tits aren't hurting and usually by now, they are in so much pain. Usually once I start bleedin, it don't stop if it's AF. I'm not under any stress. Please help.