I wish you felt better. I know what it feels like to be consumed by intense dread for so long that you become physically drained. As mentioned above, staying in the moment can be your saving grace. Try to focus intensely just on your breathing and do not let any thoughts/analysis in while you are concentrating. Soon you may be able to feel relief from your mind and emotions, and may even feel calm. If you can accomplish this, do it as many times a day as you can. This will help build your strength back and allow you to feel moments of connectedness to life and your friends/family again. Also, try eating well, and even try to get yourself excited about
dishes that you really like.
From your post, it sounds like you have not lost your job, so do not try to deal with that hypothetical reality before it even occurs. I know you said its hard to smile, but try as much as you can to smile at everyone at your place of work, and possibly, after a while, you may start to mean it. In reality, you will actively be decorating your surroundings there with your grin, and people will reciprocate.
The doom you feel right now is not the way things really are. Life is beautiful, I swear it is. Those of us that suffer from depression are just burdened -- at some times more than others -- with a very ugly screen that inserts itself between us and the way things really are. I really hope you can poke some holes through that screen soon and eventually tear it apart.
"Even when the sky is heavily overcast, the sun hasn't disappeared. It's still there on the other side of the clouds." - E.T.