Miss V - I first got my BFP on the day my period was due, 14dpo, and used a CB (same one you have) and a FRER. both lines were very faint that my husband wasn't very convinced
I tested again the next day with another FRER and some IC and there weren't any lines - I obviously went into panic mode!!
I sent my husband out to get a CB Digi and although my lines on the previous tests had been really faint, the CB Digi said 2-3 weeks. My husband couldn't argue with that 
I continued to test through the week and month and when I hit about 18-19dpo that's when my lines starting getting darker and there was no questioning it 