Of course you have changed! You are also in shock and have been traumatized!
I remember when my brother in law died suddenly, it left me really shell-shocked for about 6 months though I would say it was more like a year before it didn't affect my mood daily.
These kinds of things are not like when a sick, old person dies, though those things are hard, too, it isn't quite the same.
I am so sorry for the loss of your neice and I hope the family can do right by her baby, that little girl has lost so much before she has even realized what she had. That makes me so sad.
Work through your grief the best way you can, and tell your husband how you feel, he may be able to understand, at least on some level, to give you the space you need to get to a healthy place of acceptance, where you can continue living.
It doesn't happen overnight.
My thoughts are with you and her family,
Liz M.