"Magical Thinking" How I might have coped with death

Good Evening =]

This question is going to sound a bit bizarre, but it would really put my mind at ease.

When I was about 7, my grandmother died of pancreatic cancer. She lived longer than she was supposed to, and this is because my grandpa and parents took good care of her. On the day that she died, I remember she was in my grandpa's house for a little. I got a chance to say goodbye to her before my parents made me and my siblings go to the park. When we came back from the park she was taken away, and she died that night in the hospital.

When my mother told us the next day, I was shocked. I started laughing. I remember not really understanding or coping. The funeral came and went, and I guess that as a child I didn't deal too well.

I was sitting in my room a week later, and I started thinking "what if I killed her. What if it's my fault?" and I started fabricating ways in which I could have taken her life that day. I convinced myself that I was the cause of her death, because I did something to cause it. I fabricated many ways, all of which were concrete ways. Like pills. Or playing with her machine. Or things I'm ashamed to even say.

I think some deep part of my psyche still blames myself for it. I know it sound sick, but I spoke to my mom and sister who were there that day. They said I wasn't ever alone with her, and that nothing I could have done could have caused her cancer.

I was diagnosed with generalized anxiety disorder and OCD. How do I put my thoughts to rest? Is this a part of what I have?

Thanks!

-FP

I'm not sure how to remedy it... this is close to the way I "deal" with death as well.
My 1st & only at the time, dog died a very lengthy death from heart failure which made her wheeze all the time & struggle to breathe. My parents bought her 1000's of $s worth of medicine & we even had her on oxygen a few times at the pet ER.
I had her since I was 3 until 13. She was my only real friend then. I thought maybe what I fed her or pulling on her leash, etc could've caused it.

3 years ago, my best friend, who's like a sister to me, was shot & killed my her ex in her driveway after coming home from a concert she had invited me to attend with her (& most likely spend the night at her house after). I feel guilty not doing something about him, I feel guilty not being there (as if I could've stopped it?).

When my LI fiance was deported, (while I was away visiting my parents), I felt the same way, like I could've stopped it had I been there, or somehow I caused it.

I feel that way anytime someone I love gets ill, etc. like I could've stopped it had I been there, or I caused it somehow, or maybe I did something to cause punishment oreven a curse of knowing me?