Before I post anything, I just wan't to let you know that I'm speaking about personal experiences and it may not apply to your situation.
I too had those episodes of feeling content, often during the timespan when I was engaged with a good book/game/series or sometimes for no reason at all.
However they were only a symptom of my condition, rarely lasting longer than a few days and then everything came crashing down again.
It finally changed when I finally managed to find a competent doctor, got diagnosed and medicated.
While it was obvious to me that I was depressed, I would have never thought that I could have social anxiety. I was aware of all the symptoms, but I simply wouldn't draw the conclusion.
I spent a lot of my time overthinking everyday events, or planning out for every eventuality of an embarassing situation. It was quite the obsession and interfered with my everyday life.
I would get easily lost in thought mid-sentence while reading a book, only to realize that I just read a whole page without picking up any content.
Every kind of social interaction was being hindered by crippling fear of doing something wrong.
The only thing I can say is that medication worked for me and those two issues are gone for now. An appointment tomorrow will decide further course of action.
Of course, none of this might be of any relevance for you.
You may indeed be ok now and be able to recover on your own, in which case I congratulate you for being a stronger person than I am.
Just don't hesitate of getting professional help, should you fail to pick yourself up this time.
It can really work.
This isn't everything I wanted to say right now, but I'm posting using my mobile, which makes structuring difficult.