Faint lines no AF !!

Sharni • Married my best friend on 5 October 2013. Lost our first baby 15/01/2015 at 19w2d.LGH now due with 🌈
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 !!