I need help or ideas

So I have come to the conclusion a while back but haven’t done or said anything hoping it get better. My fiancé has a drinking problem. He sneaks it an he used money we were suppose to use for an oil change for alcohol. If you confront him he denies it an gets really upset that I would even think that. I’m trying to get him to stop only because he drinks to the point where he can’t move his legs an he crawls everywhere basically. I don’t want that near my son not do I want it around our unborn child that is due in March. Is there any ideas or helpful tips that will help me in any way to get him to slow down a bit.