The best thing you can do is talk. Start by telling your partner that you are worried about them and that you think they have a problem. Have evidence ready to back up everything you say. That makes is much harder to deny. Then tell them you think they should get help. If they refuse, there are groups that can help you. Just remember that you have to think of yourself in this situation. You can get help and support but is someone is not ready to get help, there is not much you can do. If you want to know more, there is a great blog about this at http://www.lifeworkscommunity.com/news/blog-wordpress/starting-the-conversation-adiction-depression-and-eating-disorders-2/
First things first - go to Al Anon, and be kind to yourself, and keep reaching out to people who know how your feeling. Prayers are with you.