I also want to echo what rootatoot and showofhands have said. I do understand that some of the other contributors are speaking from a place of desperate hurt and loss that I have not experienced and could never judge, and maybe OP did not choose her words carefully enough. But posting here is a way of trying to work through feelings and she does realise already by the sounds of things that these are not 'acceptable' feelings. Sometimes 'unacceptable' feelings can ambush you from nowhere.
Just to share my experience, I have a DD (now 4) and am 7 months pregnant with DS (according to the scan, anyway!). I didn't think I cared about the gender of this baby but asked to know at the scan because DD was so adamant that she wanted a sister and I thought we should prepare her for the other possibility. She was a little upset and then adjusted very quickly and I think it was the right decision for her. I, however, was unexpectedly very upset and was in tears for days - but did my best to conceal it because I knew it was 'unacceptable'.
I have thought through the reasons why I was upset, which are many and think I have worked it through - I don't feel upset as such anymore and know I already love this baby and will do so more and more as I get to know him as an individual not as a gender. However, I do still have some sadness, which I hope will go over time. I agree this in no way comparable to the loss of a baby and it would be trite to even try to compare it, and having struggled to conceive this baby for 18 months (and lost a pregnancy previously) I am very aware how lucky I am to have him. But I don't think OP was trying to compare her feelings to losing a baby, even if the word 'devastated' suggested that to some.
Cherryberry, would you consider trying to find out the sex of the baby? If you feel this way it might be better to work through the feelings now rather than when the baby arrives? I am really glad I did, even though it was hard for a while. Either way I know it is hard to deal with unacceptable feelings. I found there are quite a few resources and discussion threads on 'gender disappointment' (try googling that) to be found on the web which did help me process my feelings, even if it seems that support is thin on the ground on Mumsnet. Good luck and I hope you find a way to feel positive and enjoy your pregnancy and your baby when s/he arrives!