What Causes Delay In Periods After Taking Novelon?

Hi. I had a miscarriage in May. Then I had a regular period in June. After which I started taking Novelon. I completed the course. However I missed one tablet in last week but took it next day as instructed. Now it s my fourth day after completing the course but I still have not got my period yet. Is there any chance of pregnancy? I m worried as I am not ready for it. Please reply.