I hope I'm not risking breaking the rules here about medical advice, but, I can say without a doubt that when I was drinking I was depressed: alcohol is a powerful depressant of the central nervous system as well as having various effects on the brain. Mood swings being one of the first effects...
could be the alcohol that has you feeling down?
About rehab: I have never met anyone who said it wasn't a really good thing for them. And, I've met a lot of people in the rooms who started their sober journey out with rehab.
It sounds like a great idea!