Negative pregnancy test ; no period

I usually have a 36-38 day cycle. Today is the 39th day and i still dont see a decrease in my bbt which is 97.7 . Before my cycle comes on my bbt drops down to abt 97.1-96 the day of or before my cycle. I took a first response digital pregnancy test and it said -No . First response suppose to let you know at 6 days before you're missed period..i went on their website and put in my cycle length and the date of my last period date. It said that i culd  take their pregnancy test now to get accurate results so i took it and its negative... So is it that i may just not be pregnant and im just skipping a period?