Well, yes, it's possible that you saw evap lines.
The thing is, constipation, more frequent urination, heartburn, severe cramping, and extra discharge aren't symptoms of a healthy early pregnancy.
Constipation, frequent urination and heartburn are symptoms of late pregnancy, caused by the size of the baby pressing on your organs. Severe cramping indicates you may have a period on the way that is a little late, and heavy.
It seems very unlikely that you are pregnant at this time, and can probably expect your period to start in the next few days.
Anything is possible, or it could be a chemical pregnancy, I'd wait a week and retest.