What does this mean ?? COMMENT PLS

I took 4 pregnancy tests within 1weeks span. The first one (one the metal thing) was completely negative, the second one showed a line that was kind of faint but still clearly there, the third one also had a faint line but it was VERY faint, and the 4th one (I don't have a picture of it) but it was completely negative. Does anyone know what this could mean? I tried to search it but there were no articles about it anywhere that I could find. Am I pregnant? Why did my test come out in this order ? Why are they like this ?