What are the chances of getting 2 positive HPT and then a negative?

I have PCOS and was late by a week this month. I tested using AimStick and it instantly came back positive even before the control line was able to show up. Instantly I took another test that was given to me by my friend who works in a doctor's office. I only had a few drops of urine to give but it also gave a positive reading. Both tests were faint lines but even my friend read it (she is a nurse) and she said it was positive! I was elated because we have been trying for over a year! Today (3 days later), I took another test given to me by my friend from her work, and it came back negative. All of these tests were taken in the morning to get the highest concentration. What are the chances of getting 2 positive HPT and then 1 negative HPT and it actually be negative? My docotor is taking his time getting back to me as I await a blood test. I will be crushed if it ends up not being real because I have been thinking nothing but babies the last few days. Your advice would be great!