ON says its a girl but Im not sure... Help!

Charlene • I`m 28, wife to the most amazing hubby, a mom to a handsome 4 year old boy 2 year old baby girl!
We have a 18 month old boy and expecting our second. The OB says its a girl for sure but I cant see it clearly. With my son we saw the goods at 13 weeks. But part of me still wonders if it is truly a girl. What do you think?