faint positive this morning.line disappeared this evening

took a test at around 10ish this mornin and faint positive come up straight away before the 5 mins .been relooking at it on and off throughout the day and was defo a thick pale pink line but just looked at7pm and it's just a badly faded control line and barely visable test line.help what does this mean?pic was taken when I took the test this morning .waiting for the morning to retest but currently stressing and confused