I have been where you are...there were days that were so black that i couldn't bring myself to get out of bed. I thought why should I be part of this world. But my wonderful husband reminded me that I had a family that cared about me and my pets cared about me. I don't know if you have children but that was also a motivator for me to get help. Go to a therapist, or pdoc. They won't bite you and after a couple of sessions you may find that you are starting to feel a bit better.
Also, see about taking meds....the right combo can also help bring you out of the funk. It won't keep it away but it will prevent the downward sprial we all experience.