CB digital advanced OPK problem

4 days flashing smily and 2 days empty circle

Details:

CD 10-13: Flashing 

CD 14- had to use new holder due to error (book symbol indicating get new one) 

tested again after holding for at least 4 hours (2x) got empty circle all day

CD-15 empty circle with first morning urine 

 From days 10-13 the second line on the urine stick was lighter than control but I could see it pretty well. 
days 14-15 the second line seems even lighter than before. 
Also, egg white cervival mucus was obvious on CD 13-14.

 
so what’s happening? Should I keep testing? Have I already ovulated? I’m really confused.