If the death was sudden, violent, or witnessed, you may be carrying trauma alongside grief. They're different problems and need different help.
Trauma signs: intrusive images you can't stop, nightmares, hypervigilance, avoiding places or reminders entirely, feeling like it's happening again.
Grief work asks you to approach the loss. Trauma work usually has to come first, or approaching just re-injures you.
Trauma-focused therapies — EMDR, trauma-focused CBT — have strong evidence. This is one of the places where professional help isn't optional extra credit.