I've never heard of waiting until the sunday after your period to start birth control pills
The ones i've ever used (in uk) say to either start taking on the first day of your period and you are then covered straight away (assuming you don't have sex during your period) or start anytime but use an additional method ie condoms for seven days.
This isn't just what I have heard or what my doctor has said but from the leaflet in the pill box itself
if you have used condoms and are sure they didn't split and you followed the rules ie no contact unless condom on, etc. Then I wouldn't expect you to be pregnant.
But take a test anyway, but as it is nearly 8 weeks (my lmp was june 1

I would see your doctor to find out any underlying cause as to why you may have missed your period.