Sorry that happened to you ((Melissa)). My heroin-addict dad also committed suicide by shooting himself in the head. That was a little over two years ago. The pain does subside, ever so slowly... it is confusing, losing someone to suicide. When I get fed up with not knowing the answers, I write all my questions out and reread them. When its before my eyes, I can realize that I will never have the answers to my question and relax enough to let it go (for that moment/day). It's tough, many healing thoughts to you.
I do not feel guilt over my dad's death, not anymore. More often I feel abandoned, like I'm being punished in some way. All the feelings you have right now are valid, but know that they are not the truth (ex: feeling guilt, like you caused your mom's death when you absolutely did not).