Oh Jet, I'm so sorry to hear that. Do you live in a city, or in the countryside? I understand how going out mightn't appeal right now, but if you've a park nearby where you could have a little walk, and get those endormophins abuzzing, you might even get a little benefit...
But each thing in its own time... I hope you have some good friends around you... and we're here too!
"Guilt" isn't an easy one to deal with and I think most people who do lose someone illogically do feel that sentiment for something or other. I know when my grandma passed on, I felt it for not having written more regularly etc etc...
With my the death of my Mum, I was very low - I couldn't see how life could ever be "right" again... I had no memories of before her illness, and could only picture her ill in my mind. I couldn't even share with family, as are family aren't "like that" and it was each person in his own corner keeping a stiff upper lip.
But, in time, everything does seem to work its way round... I still miss her tremendously as we were very close, and it's 13 years since she passed on, but the time I spent with her during her illness I now treasure... and I could see images of her "before" within six months to a year of her passing.
I now have lovely memories, and treasure those special moments I spent with her, nursing her, and regret nothing...
I hope you find some inner peace too... but these moments we have to live through unfortunately; each person in his own time.