Birth control question

I've been taking the combo pill for three years now. But I have an odd question: are you still protected against pregnancy during your sugar pill week? 
I ask because I had sex on my period, and we use my birth control and removal. I started my pack as usual, and the 9 days after we had sex on my period I had one instance of spotting (VERY UNUSUAL FOR ME) it was dark reddish brown and was one instance. I'm worried it might be implantation spotting.. Advice? 
-worried college 20 something