positive test but got period?

My period was late by 10 days. I took pregnancy test a few days after the 5th day and they all came up positive. (The pink dye) then after the 10th day I got my period? The first day was super heavy with big blood clots and then after the first day it was light where I didn't even need to wear a tampon and little blood in my pad. I'm confused on why the tests were positive but I got my period?