I'm LATE an CONFUSED

India

So my body has been acting real weird an My period (sorry I don't know the terms for these) is pretty much 3 days late, so I took a test, the test is Negative an I'm confused I've never been this late before 3 days is a long time for me. Can anyone tell me if there could be something else that could cause this lateness or did I just take the test too early or something?

PLEASE HELP ME.