faint lines

due March 1st with baby 3. I am 4weeks 3 days according to Glow. I am still getting very faint lines even with fmu or a hold. I have had some spotting on and off. never on the panty liner only when I wipe happens once or twice a day since Wednesday. spotting is brown. should lines be stronger now? anyone one else experience faint lines at 4 weeks? line has been the same it wasn't that I had a dark line and then a light line. i didn't spot with other pregnancies. on Friday nurse stated that spotting was normal and nothing to worry about if not on pad. any thoughts?