3 days w/BFP OPK's...is this normal?

I test often, but am still unsure how these actually work. So I have had 3 days in a row of positive opk's. 1st day was a little darker than the control, yesterday the lines were equal in color and today darker. Is it normal to have positives 3 days in a row? I have no other symptoms of ovulation. My temp actually went down and hot flashes...but that's about it.