Insurance doesn't cover blood test

Okay so I'm very annoyed right now because I just had my 12 week appointment and they said my insurance doesn't cover a blood test to find out the gender. I just got done talking to two other friends of mine who have the same exact insurance and they just had a blood test done two days ago (they are both 12 weeks as well). I'm like really furious cuz this is a prime example of why I have bad luck. I'm trying to not overreact but I might "threaten" my doctor by saying I will have to switch doctors then. I really hope they just give in cuz I don't feel like switching doctors. Ugh