Oh Blue Cat, I gasped when I read your post. I am so sorry! I can't imagine how horrible it must have felt to deal with that alone, but I am very glad you took care of yourself and reached out for help here- it's strange, we don't see each other with our eyes on this board, but I sometimes think we can feel with our heart even better when we are not distracted by appearances.

A long time ago, a close friend of mine killed herself, she shot herself in the face, and I kept asking why why over and over, and tried to think of the signs I must have missed, and what I should, could, would have said if I had known she was going to do that. She killed herself the day before we were going to meet and have lunch, and I was so mad with grief I blamed myself- I should have made plans with her sooner..etc. When someone dies from an accident or illness, it is painful, but when someone takes their own life, it is excruciating for those loved ones left behind. Please know that it is natural to obsess over all the what if's, and also that there will probably never be the answers you want to explain why. It just is.
You will be recovering from this for awhile, so be extra kind to yourself. Grief is the most human of emotions I think. It rips you open, but if you are able to eventually heal, it will bring you strength - just knowing that you can survive a loss of that magnitude.
The next few weeks are going to be really rough, I hope you will post often and cry on our shoulders whenever you need to. I'll be holding thoughts of you in my heart-