Hugs. I know how hard it is to be with someone who is always down.
I wonder (and forgive me if this has already been addressed) does your H (to use the in-vogue term) *own* his unhappiness? Or does he blame it all on you or on other external circumstances? Does he think that somehow it's your responsibility to "fix" it?
Or is the pressure to make things better more internal? That is, it is you who feels that you *should* be doing more to help someone you care about and feeling frustrated/angry when your strategies aren't working?
Also, for me, based on my own personal situation, (and, again, forgive me if this has already been discussed to death) the excessive drinking sounds like a huge RED FLAG.
My H always said that he "needed" to drink or "deserved" to drink because he was so unhappy.
I could never explain in a way that he would listen to what seemed to me a glaringly obvious fact. He didn't drink because he was unhappy. He was unhappy because he drank.
Now, if you've made your way through my novelesque (is that really a word??) descriptions of my H's foo/background, you'll see that drinking was/is far from his sole problem. However, it wasn't until he stopped drinking entirely that he was even able to begin to understand some of his other issues. For example, although we had been together for years, it was only after he sought treatment for alcoholism and stopped drinking entirely that he was even able to tell me about his childhood sexual abuse and to consider the role that that has played in his life.
Now, I may be totally wrong (and I hope I am) and alcohol abuse may have nothing to do with your situation, but through my long-ago participation in Alanon, I've learned that, basically, nothing can get better until (if it exists) the alcoholism is addressed.
Just something to think about. And I could be completely off-base, since I'm so sensitized to alcohol abuse by my own situation.
