Coping with Complicated Grief: Seeking Advice

Does anyone have any advice to manage complicated grief? The first major death in my life was my grandma in 2015. She and I were very, very close. I’ve worked on it a little in therapy and I often write my grandma letters as if she’s still alive as a way to cope. Then in 2018 I lost my Uncle Scott completely unexpectedly and I don’t think I’ve really realised that he’s gone. I think I fooled myself into thinking I was okay but earlier this month I lost my Uncle Howie. He and I were extremely close. His funeral was a couple days ago and I lost it. His daughter told me that “he loved [me] like one of his own.” And I know that, but it wrecked me even more. My grandma and my uncles and aunts filled the space of my father, so my Uncle Howie really was like my dad. It’s hard to get my brain to understand that someone is dead. And I doubt there’s an afterlife (I’m Wiccan, and don’t really think an afterlife similar to Christianity exists). I don’t know how to understand and cope with death. Any advice is welcome. (Also, I am working with my therapist on this, but I want advice from people who understand, too.)