Menstral cycle starting earlier than normal while taking contraceptive

Patient: I have started taking contraceptive last month for the first time. My gp told me that I should start taking my first pill on 1st day of my next menstral cycle, i did do so. That was on the 8th of October 2011 there is still 1 week left before i take the different colour pill that I should be taking during my periods but my menstral cycle started 2 days ago (small flow) should I be concerned? do I need to go to my GP. Please advise

Doctor: The breakthrough early bleeding that you are experiencing in your case may be due to either :i) You are not complying with taking the drug on time. The pills have to be taken at the same time every day and any alteration in the timing may cause you to experience early bleeding.ii) Smoking causes problems while taking ocp.iii) Infections : sexually transmitted infections can sometimes cause bleeding in between periods.If the bleeding continues for a longer time or you have symptoms of burning urination, fever, you may need to visit your doctor to diagnose you for STIs and rule our other causes of bleeding.