As hard as this will be. If he is doing this right in front of you, he isn’t afraid of you knowing and nothing you say or ask of him will have an impact.
If you’re genuinely concerned about his well being, I would suggest calling your gp or 111 or a local drug and alcohol charity and have them intervene.
He will probably kick off, call you things and be aggressive but one day when he is thinking clearly and is sober he will thankyou for saving his life.
Just remember the man you fell in love with is still in there and I promise you despite the addiction he desperately wants to get out.
Be strong this is a terrible thing you are going through and always make sure you take care of yourself too. If you have a friend or family member you can talk to I’d say it’s worth opening up about things. When you’re so invested in someone it’s hard to see the bigger picture.
Stay strong x