13 days past my expected periods, My periods generally get delayed by a week, expected date was 30th june.

I tested on 5th july it was really faint line, dr said its negative and gave me Duphaston,I have completed my course still dint get periods,so i took a test today and got this after 10 mins. Looks invalid. But I could see a light line before 10 mins, thought its negative but it became strong after 10 mins and I can see dye spills.

Is it possible to get such faint lines even after so long of missing periods ? Is the test invalid?