Positive test then Negative

Sabrina
Today I know I am suppose to be. 4 wks pregnant. I took a Clear Blue home pregnancy test and it came back pregnant 1-2. I have been excited ever since but today.. I took another test just for the hell of it because I had and extra one jn the box and it came back negative. 
​Now I'm confused! I even went to get another different type test and that one said negative also. 
​What does this mean? My doctor has to all me tomorrow to make an appointment. I'm nervous what she will say :(