I'm very sorry that your family had to go through that. Depression is such a difficult illness to deal with and I can understand how discouraging it is to see a close family member commit suicide because of it.
We were stationed at Ft Bragg for several years, including when my first DD was born. I remember hearing about a PPD group there that might be some really good support. Ask your doctor or counselour and they should be able to give you more information about it. It may help to go to some meetings and be able to talk about what you are are going through with other people who have been there or who are also going through the same thing.
Keep us updated on how your appointments go!