Has this happend to anyone else

Im 17week5days and of course its vday when i get this news.... I got a call from my obgyn about genetic testing. All of them came back negative other then tube defects so that one came back postive:( im so beyond scared my ob said not to worry though that its probably nothing and when i make an appt for an ultrasound to see if there really is a tube defect.... I guess my question is how possible is it that the blood test was wrong..... On a side note i got an early test at 15 weeks to find out the gender and she said if she saw anything they let my ob know and nothing was said to the ob...omg idk im just so upset. Constant throwing up because of my little man such a rough pregnancy and now this.....