Digital tests

Hey guys,

Anyone ever had issues with clear blue digital tests? I’m 5 days late on my period and my mum suggested I did a test yesterday and she bought clear blue digital however it come up not pregnant obviously, could it be because I didn’t do it first thing or is there another reason my period could be late? I have a healthy balanced diet and my stress levels haven’t been high as I know from previous experience that can affect periods, just really need some advice as I’m not entirely sure what’s going on 😂