What Causes Delayed Period After Having Intercourse While On Femilon?

Hi Dr. Chetna,

My name is mamatha and im 24yrs old. I got married 3months ago. im using femilon tablets for my pregnency control.

I have started using this on july 23rd 2010 which was my first day of menses. I have continued for 21 days and gave a gap of 7 days and started the next strip of tablets on 20th August. All these duration I had intercourse without any other birth control methods. Till now my mensus have not started. Is there any possibility of me getting conceived?

I usually have irregular menses.