Jenna -- the only way I can relate is how my mom explained how she felt after placing my sister and while she was pregnant with me. She told me my whole life how she had told everyone she wanted a boy. She called my a boy name while pregnant with me. She explained to me that deep down, she pretty much figured that God would never let her have another daughter after "giving away" one. She said that when she realized I WAS in fact a girl (and staying that way

) she dealt with many emotions (including possession and fear of loss) ...
I think what you are feeling is normal. I think that its going to be ok, you will work this through and no matter WHAT baby you have, munchkin and butterball will both know "this" as their normal. They wont be comparing to anything else, because they will know nothing else. Sister, brother, son, daughter no matter ...
Jen