Don't read old tests days later! Read it that day (preferably within the test window) and throw it out.
I do see something when I tilt my screen, but it looks like an evaporation shadow.
6dpo is far too early to be testing (so is 8dpo). Implantation usually occurs between 6-12dpo, and you'll need at least 48 hours after implantation to get a line on a test, depending on how much hCG you start with and how sensitive your test is.