Is FMU really that important?

My period is two days late. I couldn’t take a test this morning as I didn’t have any so bought some on my way home. I took a blue dye clear blue which looked ever so slightly positive so then went to get a digital & pink dye which both stated negative. I have drank 2L of water today & had a millions wees. Is it worth testing in the morning with FMU or does it not make that much difference?