Really hope all goes well but to be honest, it sounds like you are experiencing exactly what I've experienced. I started bleeding at 5 weeks 3 days and tested but the lines were still nice and dark. Had scan and from my understanding of what she said (because I thought implantation bleeding only happened at the point of implantation), basically when the egg implants, it an cause an area of bleeding. This can be absorbed, you can bleed straight away, it can hang around for a bit and then start to cause spotting (which would generally be brown/pink as it's old blood) or some people even full on bleed. I had it at 5 weeks 3 days and it lasted for about a week. Hope you have a good update for us!