Confused 😫❤️

My period is always on time every single month I’m late for my period this month I did a digital pregnancy test and it came up not pregnant...... Iv been feeling sick on and off trough the day and quite bad on a night laid in bed ,feeling very tiered & emotional I’m very confused has any one els experienced this I’m 3 days late with no sings of period at all every month i feel achey and get cramps just before my period but iv had nothing what so ever 🤷‍♀️ x