help with birth control

So I recently started birth control (Sprintec 28) I had went to the hospital for a blood clot that was about the size of my palm and i got some pretty bad news about it but anyways ever since I updated my eve app to say I started birth control (Sep 11, 2016 it was on a Sunday) my green days are gone 
and also my next period is in 18 days which I don't understand because my next pack would be on a Saturday so on Sunday do I take a blue pill or a white pill? I'm so lost please help 

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