Re: implantation bleeding?
I had light spotting a week before my BFP. To be honest I thought it was AF coming (I always spot before AF).
Then no spotting the rest of the week. I spotted on Friday 2 weeks ago and last Thursday got a BFP. I did not test before that since I thought AF was coming. But I would say at least a week after "implant" you could test and get acurate results.
It could also be your hormones with just having the new baby. Are you breastfeeding? That causes alot of changes. I spotted here and there after having the normal "just had a baby bleeding". But my first PPAF didn't happen until 4 months.