I am so sorry OP. I agree with peachy in that depressed people feel they are not good enough, not that people are not good enough for them. The hardest thing about suicide is the lack of answers to the why's.
This thead here: What to do when a partner dies is very informative about the practicalites of what to do when you lose your partner. I hope it will help to at least lessen some of your worries.
Its a good plan to contact a bereavement counsellor and your gp. 9 years ago, my brother commited suicide on the 20th of December, and as though that wasnt horrendous enough, that January, so did my best friend. Suicide is awful no matter what, but I think things are either harder when its around a time when most people are celebrating christmas and new year. You will need all the support you can get, dont be afraid to ask for it.
It will take a long long time to sink in from my own experience. When I thought about my brother in the months shortly after his death, I just couldnt handle the fact he was gone. I used to think he was on holiday. Sounds crazy I know but when you lose someone you love so suddenly, you do think crazy thoughts, to help you cope with the shock. It WILL sink in eventually though and you must allow yourself to grieve however way it comes out, cry, get angry, look at photos or hide all photos..whatever it is that helps you work through the pain.
I wish you every strength, you will get through this. You have your little DD to get through it for. x