I've always felt like that. I used to love writing and the abyss would always show up. There might be an end, either speeding away in slightly bigger circles, or just taking a leap, and hoping you can make it across the abyss.
Add worthless to that useless and that's generally where I'm at. But I agree with ferretbandit. Explain your feelings as best you can to your wife. Let her know that it's about you, not her, and that you aren't asking her to do anything other then be there for you and support you.
I'm also on Cymbalta & Lorazepam, which helps I guess. I've also gone to (and will be again) therapy. That definitely helps.
We all desire to be understood and not to have people show us sympathy all the time but to empathize with us. Empathy is based on knowledge. I would have to know how you suffer and feel to truly imagine what it is like to walk in your shoes. Because face it. No one truly knows even if we tell them but it is based on this imaginiation of ours that we can put ourselves in someones place and visualize how we would feel if we felt that way or we experienced such things. People can only do this if we talk to them about what it is going on in our lives.
I don't know if you are a religious man and how you view marriage but God said that the man and wife would leave mother and father and become one. She is your partner. The other half of you. You would not want half your body to not work, would you. If we shut down communication on things that we are feeling, we are shutting that person out, when we vowed to share our life with them. We may feel we are protecting them from the darkness. But that protection may make them suspicious about how we feel about them or what is going on with us. They need to be reassured of the love and trust that we have in them. If this partner of yours is a loving person, she will truly want to know how you feel. She would not want you to be someone she doesn't know. That would not make you any different then the neighbors around you. We all have to trust someone. Who better for the job. Our spouse and the ultimate listener, God.