How do I forgive myself?

I’ve done something awful and I’ve been sobbing all day and night for months. I cry out to God for forgiveness and mercy but the pain doesn’t go away. I know that God has forgiven me but I don’t think I can forgive myself. What do I do? Suicide sounds like the only way to silence this guilt and shame I feel. I know that suicide is a sin though and it’s honestly the only reason I’m still here. How do I forgive myself?