Grieve for however long you need to. I believe you can move forward from this. Moving forward does not mean forgetting, but instead remembering your son, keeping the memories and the love you have for him, in your heart whilst also getting on with life
Also sometimes time alone heals but if that is not the case then you need something else besides time. That something else is, you purposely giving yourself a self talk about moving forward.
Are you seeing any mental health workers? Maybe that could help?