Faint line on test kit and 3 days later it almost gone

Hi all moms! On 6 sept I did a test then it shows a faint line ( very light ) immediately after I dip Then to confirm … 3 days later I did the test again from the same brand but this time around the line seems almost invisible and lighter than previously done test ! FYI; second test done in the morning :) Any idea what should I do next ? Could this be just an error or chemical pregnancy ? Thank you in advance :)