Ok soo I got a blood test in my doctors office to check for everything and along came with it came the gender check

Test came back that it was a girl BUT I don't believe it !! I just been having this strong feeling that it's a Boy ...I already had 4 girls 3 living and 8 months ago I had my first boy and I'm pregnant again and it really feels like a boy ... I guess I have to wait for my ultrasound to reveal the truth ... Can the blood work be wrong or they missed the Y chromosome??????????