How long after possible implantation bleeding should a hpt show up positive, it's the first bleeding post partum so i have no cycle to go on. and why would the spotting stop for 12 hours then start back up only to be pink and smell like lochia?

1 week late: Home pregnancy tests become positive at about the time when you're one week late.

3 weeks post-sex: Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully