So in short you are missing friendship, companionship, which would complete your happiness circle.
Two words: Love Life.
How you ask ?
STEP OUT OF YOUR DAILY ROUTINE ! make the effort to do what you dont usually do right now, go help the needy, go help those unfortunate (and God knows there are a lot of people in hardship), give your free time to others, be an inspiration to them, give them hope, cheer people up, there is no reasons (as you have point it out to yourself already) for you to be depressed, you have everything that other people dont have...
Love, Friendship, and Happiness WILL come to you once you have given enough back to your community (i am not talking about money, i am referring to giving your honest time, your honest effort, your feelings and knowledge from your head and heart...)
Learn about buddhism, learn about christianity, learn about other religious faith...
... or join a star-gazing group
Dont do anything expecting for love or friendship .... that's selfish...(even tho that's what you want, i know it's contradicting)
but save yourself the trouble, expectations will set you back into depression...
you dont want to waste your time being how you currently are again...
if what you have been doing is wrong or is making you not happy: Change !
Change for the better bud !
You will be fine