5.5 weeks pregnant - line starting to fade

Hi everyone

found out I was pregnant at the standard 4 weeks. Line got darker over the week very normally. Had my first antenatal bloods on Weds and got a text from my GP yesterday to book non-urgent appointment. Obviously straight away I did another preg test and the line was fainter, this morning the line is faint again. Please help. I’m stressed! 
I’ve been sick with a shocking cold since finding out I was pregnant, so I’m crossing my fingers it is still viable.