The "whys" Are Killing Me

I found this site last week and I have to say that it was definitely what got me through the week. My beautiful 3-year-old Labradoodle was hit by a car and killed two weeks ago. It was due to a series of unusual events that has left me questioning everything. I know in reading the forum that this is normal in the grieving process but truthfully there is nothing to justify taking my Bailey from me. The first week I went through the motions only because I had to. Bailey came to me while I was going through the tragedy of losing my husband suddenly. She helped me through the loss of two wonderful dogs in 2008 and 2009 and now she's suddenly gone. I lost my dad in June and she was my support then. I am so heartbroken. I feel like I'm being punished but I can't figure out for what. I'm going through the guilt of not being there when she was running loose and then wondering if she died suddenly or suffered after being hit. I am so angry today and don't know how to handle it. I live by myself so that doesn't help. Please...someone help me through this.