BFP before Implantation

Is it possible to get a Faint Line BFP before Implantation? I have several faint lines on FRER but am brown spotting and cannot get a positive on digitals and getting VVVFL on cheapies. AF one day late now, 15 DPO (if Glow was exact on that date - could be off). Regardless of dates being correct or not, my concern is the brown spotting after I've gotten faint lines and I'm not getting darker lines. I've posted a lot lately, but I'm just nervous and scared because I had a miscarriage in the summer.