Hello! Has anyone tried the baking soda test?

Hello! Has anyone tried the baking soda test? My period is 14 days late, my cycle used to be regular. My last period was on June 6, 2020. I have dragging pains in the lower abdomen, my lower back hurts, etc. Today I did a pregnancy test — a second line appeared and then disappeared, I couldn't understand what happened. Then I tried with baking soda: the soda settled as sediment and didn't foam. As far as I heard, if it foams then you're not pregnant, if it doesn't foam then you are pregnant. Has anyone done this kind of test? How accurate is the result?