Why I can't find a job? I am going Crazy!!!!?

I got my MSc and BSc in Genetics and Molecular biology 10 years ago, in UK I worked in biotech and computer business development for 7 years. Then I came to US, did PhD for one year then had to relocate. After that I worked for a Research Institute as a research assistant, after a year, the funding ran out. It's been 6 months that I am applying for any type of job possible, business development, sales, marketing, research, laboratory, anything, even the $8 an hour inside sales jobs, but I can't get anything. I have been unemployed for 6 months. I am going crazy. What's my problem? I live in San Diego,,,, my husband works as a retail manager and I have a 4 year old daughter. Why can I not find a job?