I covered up my husbands role in my childs death for two years
That sounds very stressful. Why would you cover up your husband's role in your child's death?
He wasn't the only one to blame. He was just the last one.
Your dead child deserved justice and if your husband had something to do with it, he should be held accountable. Talk to someone about this and see if there is some way you both can make amends for this issue.
They will find out sooner or later.
You need to just do the right thing and report what happened.  You will feel a lot of relief when you finally do.