12 weeks is awfully early to tell the gender. There are nub guesses but usually are only about 50% correct so I wouldn't take it too seriously at this point. Other people's influence can make GD so much worse. I am kind of in the same position, this is our last and I'm really hoping for a girl after two boys. We have chosen not to find out the gender and I've gotten to the point where I"m okay with another boy but I'm afraid if it is another boy I will be disappointed afterall.
What I would do is not take anything seriously until your 20 week scan. But booking a private gender scan is a good idea too, so you aren't in limbo. GL, I hope you get your boy!