OPK trouble

Courtney
I'm not getting a positive OPK!!! I'm testing twice a day, once with FMU and once anytime after 2. What am I doing wrong!? 
I'm a week past my expected fertile week now and it keeps getting pushed back cause I keep recording low LH
anyone else?
Also, I'm saving the sticks so I can compare day by day. How is that any different than saving a HPT? they look like they get lighter by the next day so I don't know if theirs accurate anymore. 
SO STRESSFUL!