Late Period but 3 Neg Tests?

Cassondra

my period is late this month, I have been having unprotected sex but all 3 tests came back big fat negatives. The first test was a joking one before my missed period 1/10/2019, second one was bc my sister made me, 1/17/2019 & the 3rd bc my period still didn’t come yet 1/20/2019. Sorry for all the screenshots but if it helps they’re there.

I’m only 5 days late but starting to question what’s going on with my body. Any advice is gladly appreciated. TIA😘