changing birth control and pregnancy

I have recently changed from LoOvral (with which I was a Friday start) to Ortho again (Sunday start).  I changed to taking Ortho one week after I was susposed to start a new pack of BCP.  Normally my cycle has been pretty normal taking the LoOvral, but I have started my menstral cycle at the start of a new pack (during the first day or so). I know that LoOvral is stronger than the Ortho pill, but could this change my cycle so quickly? According to my previous cycle on the LoOvral, I was due to start my period between Aug 1st and Aug 8th which would have been the first day of a new pack.  Since I have changed bcp, I am now on Sunday start, and am due to have my period sometime this week Aug 11th - 16th.  Am I a week late, or on time, considering the new schedule?  I took an Equate pregnancy test on Aug 7th that was negative. I do feel like I could be starting my period, but often have those feelings when I am concerning about being pregnant when I have been pregnant in the past.  I know stress doesn't help any, but I would like some advise.  Thanks.

[tonysmom]

Many times, when you switch pills, your hormone levels go beserk and decide to do their own thing.  Back in November 2002, i came off of Ortho due to an allergic reaction, and missed a period.  I thought i was pg, but it was just my hormones adjusting to the new levels.