I'm so sorry. When you know that death is going to come, it's hard enough; when it happens unexpectedly, it throws you for a loop.
My DIL'S dad died last year. They were extremely close. Although her stepmother (who helped raise her) is still living and they have a wonderful relationship, it was her daddy who took care of her after her mother was killed by a drunk driver when DIL was a baby. She was his only child. She considered him practically her best friend, and she still misses him every day.
My mother, on the other hand, died two weeks before her 98th birthday. Her health had been declining, so we knew it was just a matter of time. Even so, there was a huge hole that seemed devastating. Time has made everything easier, as time does, but you don't forget - you adjust.
This is the best time for you to start recording (writing or speaking into a recorder or both) all the memories of your mother and all your family history that you know. Don't worry about doing it in any order - that can be taken care of later - just get it all down! Stock up on some hankies because you'll probably cry as you do it, but do it. Get your dad to talk into a microphone about your mother.
Pick his brains. Write up a list of questions to get him started; make the questions one you think a child might ask! That helps get the details out. The towns where your mother lived at different times are one thing, but you also want to think about what the house she grew up in was like, what she ate for breakfast, what she did at school, what she did after school, what music she liked as a teen - anything you can remember her talking about. While you're at it, get your dad's history, too.
I found this a great project to help ease my feelings when my father died suddenly. It has been more than thirty years since that happened (I was 32 then, by the way), and I'm so glad all these things were written down before my mother started forgetting them.
Do you have older friends in your neighborhood or perhaps at your church (if you have one)? Would an older woman whom you love and respect be willing to be your other mama for a while? It's very comforting to have an older woman to turn to sometimes.