It's a boy... Why do I feel so :(

I know this is completely irrational and I'm an so thankful for my healthy baby.. But today we found out we are having a second boy and I burst into tears!!! I had convinced myself it was a girl and now I feel so guilty for reacting this way.. But I can't shake the feeling.. Is it wrong to be a little disappointed ?? Any one else felt this? Or maybe it's just crazy Prego hormones...