PLEASE HELP, DESPERATELY NEEDED-1 positive pregnancy test, 3 negative

Sophie
Basically first positive(took it at midnight)  it came up with the line in the square to be a bold line and the line in the oval was very faint and as time went on it became bolder, so meaning I was positive. 
Then I took another test yesterday in the morning at a clinic(after a few hours of a positive test)  came up negative again I took another test today and it came up with just a line through the oval, and I'm just confused with what's going on, cause I know a false positive is really rare and I'm not too sure with what I should do. 
I had two tiny spots of blood and nothing else.I have no pain anymore, my breasts don't hurt, I have an occasional stomach ache. Any advice?