Pregnant / failed plan b ?

Hello, has anyone took a plan B got what you thought was a period almost a week before it was due then still ended up pregnant ????

I took a plan b around the 10-11 of this month a few days later then started brown spotting then turned into what I thought was my menstrual cycle It was pretty heavy but not like usual heavy clots ect….. (sorry for the tmi) but that was alittle odd for me and only last about 4 days so a couple days ago I started taking home pregnancy test and they alll have had very faint lines on them 2 different kinds so I don’t know if to believe I might actually be pregnant has this happen to anyone thought was a period after plan b and still ended up pregnant??