Pregnancy test not getting darker

Lola

Hey ladies what do you think is going on I have a doctor's appointment tomorrow but was wondering why my test isn't getting darker today would be the 3rd day of testing and it got a lil bit darker on the second day but the 3rd day it's gotten a tinge lighter my opks are still coming up positive as well I'm not sure how many dpo I am because I got almost positive opks anyone else had this happen to them and was still pregnant