I recently lost my ex

My ex died in a motorbike accident three weeks ago. Although I am in a new relationship we were very close and I don’t know how to cope. He has been buried - I couldn’t face the funeral - but I have been to the grave to see him. I can’t talk to my partner as he is jealous and can’t understand why I need to grieve or why I feel sad. I feel alone in my thoughts and don’t know how to cope day by day.