What Causes Menstruation While In The Mid Of The Microgynon Pack?

I am 18 and have been taking the contraceptive pill, "microgynon 30", for the past 10 months. I have taken it at the same time each day and have never missed a pill.



I was told that if you wished to prevent a period you could take two packets back to back. As I was going on holiday twice this summer and my periods happened to occur during the time which I was away I decided to prevent my period two times in a row, effectively taking 3 packets back to back.



On the penultimate pill of my 3rd packet my period started. This was strange as it normally takes 4 days during the 7 day break for my period to start and it started while I had not even started my 7 day break.



I am concerned by what this could mean..

Am I pregnant?

Has my body become immune to the hormones contained in the pill and does this mean that the pill is no longer effective as a contraceptive?



Thankyou for your help