I think i'm pregnant period due monday. tested yesterday & today both very faint but still positive. evap line? today's was + in 3ish min, pregnant?

The pregnancy: tests need to be read at the time stated in the instructions. You are right - that if you try to read them a long time later - that it can show as a "+" due to concentration or evaporation line. Usually recommend waiting until you miss a period for standard home pregnancy test. Or you could take an early response type pregnancy test now.