sdi, I can absolutely relate to dealing with depression, anxiety, and low self-esteem by drinking - those at the root were my reasons. I've struggled with them for 20 years, since I was a teenager. I'm only going on a month, but those feelings are the least they've ever been, being sober, even though they were issues long before the drinking began to be a problem (I was more a social drinker in my 20's, but I still think any alcohol at all probably overall negatively affected my mental health).
Keep on keeping on. I'm glad your fiancé is supportive, continue to be honest and transparent with him, even if it's just to say, "I thought about drinking today/I want to drink today," as cravings will come. Lean on him and yourself to ride those out, no drink will ever feel as good as coming out on the other side of a craving knowing you were strong enough not to give in to it.