Dealing with a spouses alcohol addiction

Kelsey • I have been trying to conceive my second child for two years... I am so happy that it has finally happend!
I'm not really sure what I'm looking for  whether it's advice or just a way to vent i don't know but please no nasty comments...
Let me start from the beginning :
My DH an I have been together for 6 years... He is 24 and I am 22, we have a beautiful baby boy together who is now 3. 
When we first got together I knew that he enjoyed partying but we were also 17 and 19... So that's normal. I have never enjoyed drinking or partying, I'm to paranoid. 
DH has had a lot of partying years ... He's been able to do whatever he pleased for his entire life.. His parents never really has control over him( I guess that should have been clue number 1) but back then his drinking was on the weekend with buddies. 
3 years ago he met a guy named Dave and they have become inseparable, well Dave happens to be his boss .. 
I mean he literally spend more time with Dave on a daily basis than he does at home .. 
It got to the point where I started buying and packaging dinners for myself, DH and Dave. 
When Dave first came around he said that he wanted no harm to our family, that he thought Paul was a great guy and wanted to show Paul how to only have 3 beers a night and be okay with it. 
Wellll that was the biggest fucking cup of bullshit because 3 turned to 6, and 6 turned to 6 and some shots and now my DH was to the point where he did not go one night of the week without having at the eveeerrr least a tall boy of beer and a shot. 
We have been trying to have another baby and after finding out that it was him and the amount of alcohol that he drinks is what was keeping us from being able to get pregnant he slowed down a lot. 
Everyday that went by was a struggle for him to not drink... He got diagnosed with severe anxiety and his doctor said that he was "self medicating" with the alcohol so he gave him some medicine to start taking... But the medicine isn't fixing his craving for a beer, it doesn't keep him from craving a buzz.. And he thinks that he doesn't have a problem, he says that he choses to drink because he enjoys the taste if alcohol. He also says that he hates getting drunk but that it just ends up happening. 
We are STILL trying to conceive our next baby but we were told if he doesn't stop drinking out chances of having a baby are no better than 3% 
I don't know how else to support him or encourage him or shy him away from drinking.. 
Has anyone else delt with a spouse who wants to get away from alcohol but has an extremely hard time doing so? 
I want to support him and help him through this but how do I do that for someone who keeps disappearing to get fucked up with his piece of shit boss? 
And if you are thinking that he may be gay, I can't 100% assure you that he is not. And yes your going to say "yoi never know.. But if there is one thing I'm 100% about it's that he's not gay. And we live in an EXTREMELY small town so if he was cheating with another girl I would know before he even got out of her bed) 
Help? Or helpless?