What Causes Delayed Periods With Spotting After Intercourse?

Hi. I came off the pill on the 12th June as my partner and I are trying to conceive. I had the normal period. If my cycle went back to what it was before being on pill, which I presume is not necessarily going to happen, I would have been due on Saturday just gone. On Saturday I noticed a tiny amount of pink/ brown blood after sex. Since then nothing has happened. What does this mean???