Faint lines no AF !!

Sharni • 3 angels babies LGH2015 , LEH2019, LFH2020 1 rainbow EPH2016 Carriers of short rib polydactyl syndrome type 3. Will be starting our IVF with PGT journey next year
So AF is now officially 3 days late 
Been getting faint lines since 1 day before AF due but not getting any darker. Has any one had this before?? I am booked for the doctors tonight. What's the chance it will show in a digital if a normal hpt isn't showing very dark !!