The difference between fmu and at night

Kellie • Mother of three and currently ttc #4 due to health issues my chances are starting to shorten every day! Staying positive and wishing everyone lots of baby dust
I took a test last night and i got a weird looking line two lines tho.. then today around 11am (not fmu) i took a different brand and it came out negative. Im going to test in a few days but what could this mean? Im so excited but disappointed that todays test waa negative.. Any advice