My question involves a background check in the State of: California

I filled out an application for an employment background check. I was asked to provide ALL jobs for the past 7 years. For the past 5 years I have run my own business. Prior to that, I worked for 9 years at a large multinational firm. However, on two different occasions, in order to make ends meet, I worked 2 other jobs, each lasting 5 months. One job was in 2003 and one was in 2006. I did not list these jobs on the application because I didn't wish to seem like a job jumper and also, because I was fired from one of the jobs(which devastated my self confidence). I know that omitting this is equivalent to lying and I have been wracked with guilt and worry that I have eliminated any chance of getting hired by this firm. A part of me wants to call the interviewer up to tell him about these jobs, but I don't want to call attention to the lie if I don't have to.

My question is: How can a background check reveal past employment if you don't list it on an application? Is there a database that would show this information? And even if there is a way to check this, is this the type of employment check a company would request? I mean, how much information could they get from knowing I worked 5 months at General Motors, or another large company? It wouldn’t show the division, or even the correct state, let alone a job title, supervisor’s name, etc. Doesn’t an employer typically request employment verification--checking my previous employers to verify dates, title, etc..?

I will never lie on another application again! The worry is not worth it! But, any insight you can share would be appreciated.