Some of the posters here are exceptionally rude. Clearly have no idea exactly how difficult it is to deal with gender disappointment.
I say that as someone who has been through it myself. My husband and I decided to try for a baby and were fortunate to conceive. I've always wanted a daughter, he did not have a preference.
I'd never ever find out the sex until the birth, it's just not something I'd ever want to do. One I think it's nicer to ind out when your baby is there in the room with you, not just on a screen. Two because I think if you do have a strong preference for a either a boy or a girl, it's easier to deal with not having what you were hoping for when your baby is in your arms, not just on a scan picture.
Anyway, we had a boy. The first thing I felt was disappointment. I wanted a girl so badly, friends were expecting girls, it hurt. I thought "why did we not get our girl"? Of course over time I dealt with it (on my own, with no help professional or otherwise), I had to. Don't misunderstand I adore my son, I did from the second he was born, but I was still disappointed when the midwife said "it's a boy". My son is now 3 and I'm incredibly proud and I know how lucky I am to have him. And i would not change him for the world.
OP, I admit i haven't read the thread, I saw the first few comments saying your partner 'needs a shake' and I couldn't read anymore, I was too angry. I'd suggest giving him some time to come round, and talking things through calmly, and explain that in the end a baby of either sex is a blessing. I truly hope you are able to sort things out, and I wish you all the best.
To the rude posters: this was not easy for me to write, its taken a lot because I know how easily people judge this sort of thing. Every day I have to live with the guilt and shame of how I felt for the rest of my life, and unless you've felt it you have no idea how difficult it is to overcome. So perhaps instead of being so judgemental, why not try offering some support and at least trying to understand. If you can't do that, there's still no need to be so rude at all.