What Causes Blood Spotting During Periods?

I am 31 year old lady. I took clofert last month and my last period date was 1st May 2011. I had 10 day course of clofert after 5th day of period. Today my period day and when I went to restroom I saw some blood spot after urine but during this there was no pain. After an hour I found no bleeding. Please help me out to understand what is the problem with me. Am I pregnant or what?