Hi Anna -
I was quite certain that if I quit drinking it wouldn't make any change in my mental health, but I was (of course) completely wrong. I find now at almost 6 months sober that my highs are generally higher and my lows are not devastating like they used to be. Getting sober was the real catalyst to being able to address issues of depression and mental health in my life, as well as physical, mental and spiritual health.
I promise if you get sober things will improve dramatically. My life is not perfect now, but I am not in a downward death spiral any longer. Best wishes to you!