Expecting one gender and getting the other

Has anyone been so certain that their growing baby was either a boy or a girl and then come to find out you are having the opposite? 
I was so certain we were having a little girl.  I had dreams of a little girl and so many other things making me feel, girl.  I just found out that we are having a boy.  Don't get me wrong I will love this little boy unconditionally, but right when I found out I was shocked and slightly disappointed it wasn't what I thought.  Has anyone else felt that way?