I hope you don't mind me coming and posting in here, but I'd just like to say that I am so sorry to hear MIL isn't very understanding. I honestly don't think she has any idea on the bond you'll BOTH have with your baby and that it will be both your baby and your partners baby!
I have no advise for you, but I wish you all the very best with your TTC journey. I hope it is a short and sticky one. As for your MIL, don't let her dishearten you or get you down in anyway, some people have no idea how insenstive they are being with things they say or do, I'm sure if you both were to tell her how she made you feel she'd be so upset she made you feel that way.
with it all. I can't wait to see your preg announcment!