I had protected sex on 18th November, took an ipill within 34 hours. I have taken two pregnancy test. One in 22nd December and one in 6th January.the result was negative. But I am not having my periods. Is there any chance of pregnancy? What should I do to make my period regular. My last period was on 6th November

You had sex... that is all you need to do for there to be a chance you are pregnant. No form of birth control is 100% effective... the iPill isn't 100% effective even if taken within the required time frame. You have not had your period so that is an indication of a possible pregnancy.

Did you take the tests the first thing in the morning... the very first time you pee that moring? If you did, you took them correctly. Your next step would have a blood test for pregnancy. They are more accurate as some pregnant women will test negative for some months into the pregnancy with the urine based test.

EDIT: And as ScottGem points out...the iPill can cause period irregularity.

See your OB/Gyn. The iPill could have interfere with regular periods. But the only way to know for sure whether you are pregnant or there is some other problem is to consult your physician.