Has anyone used these tests from amazon? They have lots of reviews on amazon about false positives. Usually I'm a "line is a line" sort of a girl, but the lines were very faint and now I'm nervous! TIA [[http://www.amazon.co.uk/gp/product/B0026RKBSQ?psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s01 dogdey amazon test link!]]