3days late.

Scared to take a pregnancy test as I had a positive last week and then negative Untill yesterday I took a clear blue test which did show negative and then I had to go into work so on my break 3 hours later I see a faint line again? Is it a evaporation line? What's going on? I've been feeling that sick I've been heaving all morning at work. Sore sore boobs, odd period type cramps which have had since ovulation. I'm so confused. Any advise on this girls?