Positive test first continued with a Negative one.

Nancy
I took a pregnacy test and it came out positive but then I took another one and it came out negative. I went to the doctors today and they did a urine test and it came out negative. I also took the time to get a blood test to make sure. I mean I'm only 18 & not trying to conceive. The condom fell when we were having sexual intercourse. 
​I'm on cycle day 26, I'm usually a 23 cycle day, I had sex after my period on cycle day 6 & 7 (March 18 & 19) and my ovulation day was on the 10th. May it be too soon to know, could that postive test be true or do the negative one wins or it could just be me scare and stress that is causing me to be late on my period....