i used to say that too...but with therapy i found the real me and i wasn't the worthless person i thought i was. being unemployed also i think adds to your sense of worthlessness. can you do some volunteer work? it may help you feel better and also help you realize that you do have something to offer!!
it sounds like you are suffering from depression from all this. i found it doesn't go away by itself. can you get some help to sort all this out? i used to get so tangled up in my mind i could not do it alone.
i just read your blog...i am bipolar also. i found these things work for me
taking my meds daily
continuing with therapy on a regular basis to learn coping skills that work!
contacting my psych. if the meds don't stabalize me moods or i take a dive.they may need tweaking or a change in meds.
being responsible for my own well being having biolar.
acceptance, but also determined to live with a good quality of life

i worked successfully in corporate m'ment in ny for 7 years after being dx'ed. i am now disabled. was in mid 40's when this happened. my life is different now but i've found news ways to remain self-confidant by doing things to keep that self worth apparent to me. sometimes i have to force myself but it's worth it because the "payoff" is there.
i know only i can control my destiny even when challenged with adversity with my biolar.
not judging you. just sharing with you things that have worked for me. i hope you can find something here to help you too.