Depression is a treatable illness, but as you are clearly aware, treating it with booze is a dead end, as alcohol is itself a depressant.
I can't say I have ever suffered from clinical depression, although I am no stranger to the low blues. The abuse of alcohol, on the other hand, I have a lot of experience with. What was once my best friend, my shield and my armour for dealing with life and for quietening my own head, became the instrument of my destruction. Bacchus boomeranged, as a great man once said, and nearly cut me down.
Life without booze, which once seemed unimaginable, is ten times better than having to contend with hangovers, blackouts, shame, self loathing, and constantly having to clear up messes of my own making, I no longer have to duck into doorways to hide from people I have upset, or who I owe money to, and I don't make phone calls in the middle of the night which I forget having made the next day.
If any of that sounds like you, you might be an alcoholic; there is no minimum age for alcoholism, and it isn't a moral weakness or a lifestyle choice, it is a chronic illness. An illness, incidentally, that often goes hand in hand with depression.
But no one can tell you whether or not you are an alcoholic - no one wants to hear that about themselves, for a start. There is a saying in aa, that you can always tell an alcoholic, but you can't tell him anything. The best way to decide for yourself is to go to an aa meeting, got to a few even, and make up your own mind whether you think you fit in there. The only places I ever really felt at home was the pub, a crowd of Saints fans after Channon, LeTiss, SRL etc smashed one home, or alcoholics anonymous.
Of course, being a Saints fan would drive anyone to drink.
Good luck whatever you decide to do, but if you feel like you're on a slippery slope, don't just do nothing. Change something.