Late period but not pregnant

Layla

My period comes every single month on the 24th on the dot. My boobs always swell a little I get cramps and I get very tired. Well none of my signs showed up and my period didn’t come on the 24th... so I took a pregnancy test last night it was negative and then today I had my period.. I’m so confused. Why was it so late? Why does this randomly happen? Iv never had a late period!