OP, your pain is radiating from your post. I'm so sorry for your loss. Nothing I can say will make it better but hopefully my husband's story will give you some hope.
When I met my husband he was 2 years on from losing his mum very suddenly, and he was only just beginning to process his grief. He'd buried his pain for a lot of that time to care for his younger sibling and allow her to grieve safely with his support. So when I found him, he was only just beginning to feel his own loss. He couldn't watch certain films, couldn't talk about his mum, couldn't have pictures up of her, and it would hit him at all times of the day or night. Holidays and birthdays were the worst, but it was there all the time for him. And he was in so much pain. All I could do was hang on to him through it and care for him as much as I could, as I'm sure your DH is doing. I did it lovingly and willingly, even when his grief made him pretty awful, because I knew it was coming from a place of pain and deep vulnerabilty. It wasn't him, it really was the grief, and like you, he was mortified if he thought he'd hurt my feelings when he was struggling to cope. He never did though, I understood.
Gradually, and without really noticing, he became more able to bear it. We're 7 years on from than now. He can now talk about his mum, and we have pictures up of her. He tells our children about her, and can talk about her in a warm positive way, remembering the beautiful talented wonderful person she was and the happy memories, not just the pain and loss he feels from her not being here. The grief still sneaks up on him occasionally, sometimes with warning, like christmas and birthdays, sometimes without any warning. One of the kids might do or say something, and he will want to share it with his mum, and he can't. It doesn't go away for him. But he copes better with it now.
Please don't be too hard on yourself, let the people who love you care for you and support you. Don't expect grief to be a linear thing, from what I've seen with my husband, it can go up and down, back and forward. And the hurt doesn't go away. But in time, and with love and support, you will hopefully be able to manage it better.