The positive sign.. [Second part to first question]?

I think a common problem with blue line tests is what looks to be a positive might actually be an evaporation line. And since your positive disappeared, I wonder if that's what happened. I would buy a First Response test or other test that uses pink and try again. The first time I got a positive was with Clearblue Easy, but because the line was so faint and it was blue dye, I bought First Response and got a definite positive. Good luck!