I think it is hard for anyone, whether they're bipolar or not, to have a string of bad jobs? That's pretty depressing and certainly not your fault! I think I'd try to think of some way to give myself back a bit of excitement/interest. Have you been to a career counselor or anything ever? Or maybe a life coach?

http://www.careercounseling.com/

http://www.findyourcoach.com/

I don't have bipolar but I've have crummy jobs I've thought I had to stick out for a bit and in that case I shifted some of my self to my nonwork life and found interests, hobbies, interesting tasks to do there (starting businesses of my own while still working, for example, or going to school). Having something else to share the life-focus like school and getting a certificate/degree, learning something new might re-energize or give hope for "different" results in the future job search.