BFN...why?

Hello fellow ladies,

So my monthly is 3 days late... But i keep getting BFN and i dont understand why my period is this late? I have regular periods every month, There's 27 days between each cycle and my periods last 6 days long.

With my son i had 9.5 months ago, i remember testing positive at exactly 4 weeks. I calculated that if i am peregnant and the tests are just not reading my HCG levels then im about 4 weeks and 2 days.

My last period: Jan, 8, 2020

Tests taken: feb 4th, feb 5th and feb 7th.

The only things I've personally changed in my life is that i started working out at home doing squats, crunches, planks etc.

Here is also my calender.