Once the POAS can of worms is opened, the lid can never go back on. I wish I could hold out, but Im an early tester.
Have you used a sensitive test? Either a FRER or some ICs are good that read down to beta of 10. It could be an evaporation line, but also could be a BFP starting out. Does the line have colour in it or is it grey? And another thing (as a lady on this very thread discovered- sorry, can't recall username)- did you check it at the full ten minutes, rather then at 3?
The tests do get darker over time, sometimes you won't see a line until the 10 minute mark. And a faint line at 10mins will look darker then next day.
Are you going to test again?