Line fading after two hours??


Took a picture within 3 minutes

I had some light spotting today so I took another pregnancy test. Unfortunately in the small town I live it the only test I could find was a clear blue rapid result. I got this positive within 2 minutes, it was faint but I'm only about 4 weeks and just got my first positive yesterday. This was also not fmu and I didn't hold my urine for hours. But why did the positive result fade to almost nothing after two hours!?