Thanks for the query.
The possible causes of your spotting are:
-Withdrawal bleeding due to stopping the pills
-Post coital bleeding
bleeding, if you had intercourse around the time of ovulation.
So you wait for tow more weeks, if you do not get periods by that time go for pregnancy
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429