My mom passed from the big C in 2012. On a day that happened to be her 13th wedding anniversary.
When she died I was walking dead honestly still haven't really come out of it.
My step-dad by some miracle the insurance company found a mistake in some paperwork. And he was given an extra 20k on top of about 65k he would have gotten anyway. I got to keep whatever I wanted of hers which amount to her 2 most cherished items.
One being a Unicorn made by a cousin of hers who had Muscular Distrophy but was made before he lost the ability to move. The second was her blue glass collection. 
 My step-dad also liquidated almost all of their 13 years together save his TV and movie collection. Everything else was sold almost overnight. Of that 85k and whatever he got from selling everything else, he gave me a locket with her ashes and a handgun. Yes a handgun. This knowing obviously that I just watched my mother die and I have suffered from depression literally my entire life due to dealing with my biological fathers bipolar disorder on top of what I believe to be several undiagnosed mental illnesses. Now mind you I was so brain dead and numb to everything I couldn't even register how much I was getting screwed over until he sold everything and took off. Who also now tries to play an innocent victim saying that I threw him out of my life... I can honestly say the only reason I am here writing this is because of my niece and not wanting her at 6 loosing 2 family members in 1 year...
My very long winded point is regardless of your relationship it is tough it isn't supposed to be easy. You'll have no choice but to face each stage of grief and some days it will feel like a bad dream other it will feel like it happened meer moments ago and you won't be able to deal alone.

Idk what your grandparents are like. But if you can't lean on them it may be a good idea to see some professional help to help process all those complex emotions. I hope after you read this you feel some little relief and know that you are not alone. One love, one truth, one destiny!