Im so confused!

I took a pregnancy test 2 days ago and it came out positive, then later on it had a dry run. I took another test the next day and it was negative. Yesterday I took another and it was negative, then I took a blood test using a pregnancy test... ( I pricked my finger) and it was positive. I took another one using blood and still positive... When I looked at the 2 that we're positive with my blood the lines disappeared... What's going on?