Question: Hi Doctor,

My partner (25 years of age; Female with no medical issues / history) and I had unprotected sex in May around the 2nd and then she took an ipill around the 3rd or 4th and got her period starting on the 6th of May 2012 which continued for 3-4 days till the 9th, I guess.
It was a fairly light period. We had unprotected sex (with the withdrawal method) on the 11th of May.

She has a cycle of 28 days and so her period was due on the 2nd of XXXXXXX
She started getting some pre-menstural symptoms around the the 6th of XXXXXXX which continued till around 10th of XXXXXXX which included lower backache, tender breasts (without pain), cramps in legs and she felt as if her periods were going to start.
And now those symptoms have completely disappeared.
She took two home pregnancy tests, one on sunday evening (10th) and the other on monday (11th) morning (with the first urine sample and according to the instructions given) and both tests have come out negative.

She is now 11 days late. Just to add, in the past 11 days, she has had some parties on the 1st, 3rd, 8th and 9th of may in which she had been drinking from a low (2-3 large pegs of vodka) to large (4-6 large pegs of vodka / whiskey) amount and had been up till late at night. Besides this she has been having a normal lifestyle with a low stress work and personal life.

Could you please advise what this delay could be because of?
Do we still need to wait some more time for her period to come? Is it because of the ipill last month?
Is it normal for the period to be skipped so many days?

Thanks doc !