Serendipity - their are gender disappointment support threads and general threads - and if you post in there (im not sure if your have already) it really helps to get you some perspective. I was shattered when i found out we were having a boy. I cried for a week and when my friends would make "you have a little penis growing inside you" jokes i would crack it big time.
Whilst you might feel selfish and ridiculous for it - if we really have an underlying "preference" there's normally good reason for it. My DP is a gamer too, but we would have had our little girl be whatever she wanted, daddy's little gamer if so be it. For a long long time i wouldn't accept that i was having a boy - and it can eb really difficult - i felt really guilty for not being happy that i had a healthy bubby - especially with it being the first, no conceiving dramas, and us wanting more kids - and feeling guilty like that is really weird - so it helps to talk. IYKWIM.
Sorry for my babble... if you are worried that you might be disappointed you're probably best to find out at the u/s. If i hadn't of, "alexander" would have been called little "maddie" all through my pregnancy and i wouldn't have bonded very well when he was born. If you are having a little girl, i still think you'll find DP will adore and treasure her, just as much with a little boy. My mum just had twin baby girls and they totally make my step-dad melt. Girls make their daddy's all gooey! And you never know about more kids either... DP wasn't sure he wanted any - and he didn't want to get married until he was at least 25 - and look at us now! =D

Good luck when you do have the scan hun, and if you do want to chat you can pm me or add me to msn or whatever!