Blood pressure readings all over the place?

Does anyone else have insanely inconsistent readings?

Whenever I go to the doctor's office, they usually get a ridiculously high number like 160/90. Concerning. But okay. Maybe that's explainable as white coat syndrome.

So sometimes I use the Higi machine at my local pharmacy. Those readings will be in the neighborhood of 140/80.

Then whenever I take my blood pressure at home, it's totally normal. I just got a reading of 110/61, which I didn't even believe until I took it again and got a similar number.

It just makes me question this condition altogether.

Why are my numbers so erratic?