I have been taking Yaz BC pills since a month after the birth of my daughter. For the first 4 months my periods were very light and regular. Since then I have gone 2 full months without a period. I have taken two urine HCG tests and both were negative. My husband and I would welcome another child, just not quite this soon!
You need to talk to the prescribing doctor about this. You may need a different ratio of the hormones to return to a normal cycle. I think just a call to the doctor's office with an explanation would be enough for a change.