Sometimes it is possible to mistake evaporation lines for a positive result, but if there is an evaporation line as well as a positive line, then it might be positive for real.

Usually they say only a result that occurs within 3 minutes is reliable, and results should only be read up to something like 10 minutes after testing.

But if it keeps coming up positive, then I think you are pregnant.
If you are still unsure, do one with first urine in the morning, or better yet, pop into the doctor for confirmation.

Good luck !!!!