No period yet on BCP's

Ok Ladies..Its been a lomg time since i have been on bc. Here is a little background:   I had a miscarriage Dec 25th, 09 started bcp Jan 5 I was on also antibiotic when I started bcp(I know they can weaken bcp), did not use a back-up method, after my first mc in may it took 7 months for us to get pregnant again so I didn't think I needed one, Any who, I finished my active pills and my period didn't start?? Today is day 3 of the green pills and no period? it has been 34 days since my miscarriage, after my first mc AF showed 27 days later, i have a 27/38 day cycle normally. Should I be concerned or is this normal?  I think my period used to come on the first green pill before when I was on them.