Sorry to hear about how you are feeling Mizzuno. I don't feel that way chronically, but i do some days still get those "what's the whole point of it all" funks. Being sober of course makes them more up front as drinking sort of stashes them away in the back room of your mind.
I don't understand depression or those things too much, but some good advice from the others on perhaps seeing a doctor.
Another thing you might try is picking up a new hobby or activity that doesn't cost much money. I've started playing guitar again since I quit drinking, and i've found free online lessons and got some very inexpensive new equipment to help me along the way. Not suggesting you rush out and buy a guitar, but perhaps find something fun that you can do that doesn't cost a lot and takes your mind off the doldrums of daily life. Maybe a garden? A book club? Volunteering at some local group?
Anyway, hope you find something...and most importantly remember you are doing GREAT work by being sober!