OPK Help

Brittany
Last month on my clear blue advanced digital OPK I had a flashing smiley from CD 13 and then my static smiley on CD 19.  I didn't start my OPKs this month until CD 15 since I had so many days of the flashing smiley last month.  I'm now on CD 17 and it's saying low fertility.  I'm using the same digital holder as last month.  Any ideas?