Heeelp please??

I took a test 7 days before I was due to catch up with good old AF because of feeling sick going off coffee headaches constipation etc it came back as a wonky positive (I think) within a minute!!- anyway 6 hours later it disappeared, took another test and it was negative took an ultra sensitive one two days later (today) and it was negative, but I haven't been using the first sample of the day as I work nights so a bit difficult could I be pregnant or does it look like an evap line??