Perspective..... What you're feeling is a matter of perspective. Take a piece of paper and write, "My life *****" across the top of the page and then draw a line down the middle of the page. Write down "pros of my life" on one side and "*****" on the other. (Be real honest when doing this.....) I don't even know you, but I bet I could come up with 25 things that you have that make your life comparably better than some other peoples.... millions of people, perhaps.
The things you think suck in your life are addressable. Friends have moved away and not kept in contact? The phones, internet, and snail mail go both ways.... you contact them to say hey and check in. Your job isn't what you expected? Change it... do everything within your poser to find the job you do want or at least a more desirable job. (my neighbor was literally a rocket scientist... he lost his job due to government cut backs... he now manages a Lowe's lumber department and has never been happier!) You think you're over weight? Go to the gym.... Everything you think ***** about your life is changeable.
Only you can make those changes. It took me better than 30 years to figure this out about myself. I wasted all of that time having the worlds longest pity party.... what a waste. Get on board... this is your life and you get to make the calls.
I am not trying to minimize how you feel.... If I can be of some help, please let me know. Another good place to start feeling better is by talking to your primary care physician.... they can help you out in a big way, but they have to know that you are having a problem. Ask for help... it is that easy.
That can happen with friends. They grow up move away, get married have kids. Can the two of you keep in contact over emails?