We had a private scan at 13+6 weeks as the hospital messed up and didn’t do a booking in appointment until 16 weeks so we would have missed the nuchal measurements etc.
We didn’t even discuss whether we wanted to know the sex as we didn’t think it was possible at such an early stage, but it was very, very clear that he was a boy!
The technician asked us on the spot, and stbxh was super excited to find out so we did, and I was glad to know, as I was convinced I was having a girl.
Strangely the sonographer was a lot less certain at the hospital 20week scan, but to be honest, the equipment was so aged and different from the private scan, I’m surprised she could see anything at all.
Sooooo, I’d be 95% convinced but leave a little bit of uncertainty just in case. There’s so much about childbirth that has a dollop of uncertainty, risk, and, on the positive side, magic (!) about it, no matter how much we try and tie it all down and make it human-controlled!
When I had ds I felt it was things like this that added that kind of ‘miracle factor’ for me! He was a boy as expected, but twice the size he was supposed to be (not to mention suddenly discovered to be breach and back to back at 40weeks), and blue eyed and bright red haired, which was completely bonkers and a wonderful surprise :)
Mind you, I was completely high on oxytocin for weeks after meeting ds, the best drug I ever had 
... the morphine did nothing compared!
This was after me being terribly sensible and dull about the whole thing, as I fully expected to be freaked out and mildly disturbed by my new born and I’d planned to ‘fake it til I made it’ to get through the first few months until it turned into a properly cute little baby that wasn’t so scarily fragile and freaky new looking.
Soooo, I wasn’t expecting the whole blast of love and bonding that happened. Knocked me sideways. I thought I had had a perfectly beautiful baby and felt sooo lucky and proud he was clearly so completely amazingly perfect. I was transfixed by him that first night I couldn’t sleep because I just wanted to look at him. In reality he was a big bruiser of a new born with lots of lumps and bumps and scratches from the birth, and a lopsided head! He could have been a boy or a girl or possibly a baby goat and I’d have felt the same. Hee hee! I think nature was amusing themselves by doing that to me :)
But the point is, it’s probably right as long as you keep a little bit of an open mind just in case. And you’ll find a whole load of other wonderful surprises as you see this little whole person born with a personality already there.
It’s good if it’s giving your dp a way of bonding with the baby, as men can feel it’s all a bit theoretical before the birth, as they can’t feel the baby growing and changing like we can.
Good luck 