Private Scan

Hi mums, im due my second in September & Im wondering if having a private scan to see what the sex is, is worth the money? I already have a little boy & I'd love a little girl.. I think this is why I'm so keen to know. I won't be too disappointed if it is another boy! I have another 7 weeks until the 20 week scan & I'm so impatient! Doesn't help that a lot of people are saying it's a girl! TIA