could not find a job, frustrated....

I resigned from my job about 2 years ago to take care of my 2 daughters, and realized that I don't enjoy staying home. Since my previous jobs (bench work) do not have much growth, I decided to change my career and obtained a MS degree in a area I'm really interested in. I started job hunting about 1 year ago, but did not even get an interview. I'm very very frustrated. I am wondering if I should keep trying or just go back to my old profession. Although it is difficult to find one even in my old profession, the chances will be higher than to start a new career.

I also want to get advices from working mun, is it possible to work on a very demanding job and take good care of two naughty kids at pre-school age at the same time? Daddy is busy and won't be able to help during work days. I started to wonder if it worth spending so much time and effort in pursuing something I like but may still fail at the end.

I had seeked advice several times in the forum and I got many nice suggestions. I belive people here will give me good advice again.