Could I be pregnant?

Ok so I had the Mirena taken out the end of May after 4 yrs of it in. I have had a regular cycle for the most part since having it removed (except I had 2 cycles in the month of July which I think was just due to stress) I have been having unprotected sex since I had it removed and basically have been ttc. I started using glow in august and have been spot on as far as when my period was to start/end ect. And I have a regular 28 day cycle. However I was supposed to start on Monday and it's now Thursday and I have had no sign of AF coming to visit. I have taken a few pregnancy tests and all are negative but I am dying over here!!! Could it be that I conceived later in my cycle and my hormones are just not elevated enough yet to show a positive or do you think AF just might show later this month or what!? Anyone had similar experience!?