I do understand how you feel. It is a weird feeling after the funeral. The person you love is gone and your meant to just get on with life, but your world has changed fundamentally. Greif is the hardest emotion to deal with, it was for me. New babies is new life and happiness in a family, death is just sad, empty and painful. I hope you have someone who shares your pain over your granddad, someone who loved him as much as you did. And wants to talk about him and reminisce with you. That helps.
And yes writing does help, so does losing yourself in movies or reading. I found socialising hard because I wasn't in that space of moving on from being sad.
Take care. Self care is important when your sad. xxxx