Job trouble?

I have a background of 3 years of Customer Service and 2 years of Retail Sales. I've been a Cashier, Sales Associate, Retail Design, Print, Ship Center associate...and I can't seem to find a job. I left my last job at an Office Depot store (by giving a 4-day notice)...because I had been promoted there, had gotten 2 or 3 good performance reviews, and was still 'part time.' I remember one week I worked 58 hours. I left on a 4-day notice because I was taking a Full-Time job offered to me by a staffing agency (it was a temp to perm position). The job didn't go so well, and I quit after a week. But now I can't seem to find a job anywhere. Is it possible that my former boss is slandering me? I've been seeking a job for about 4 months now...just any particular job (Retail, etc.). I've gone to lots of interviews, recruiters and staffing agencies have told me that they like my experience and general Resume. But I don't seem to get a job for some reason.

I'm starting to wonder if I'm getting a bad reference from my former employer (particularly the General Manager). I had heard a rumor (about 2-4 months or so before I left) that the General Manager had said he wasn't going to give a lady employee a good reference from her job there. Because she was leaving on a very short notice (I think several days or so). So it doesn't surprise me. I've been considering trying this place at checkmyreference.com for $29 to see if they are slandering me and have some kind of proof/transcript for an actual company to prove that they are saying something slanderous and/or personal opinions about me.

There's a very easy way to find out if your previous employer is giving a bad reference. Have a friend or family member call them and act as if they are doing a reference check on you to see exactly what they are saying. If you're sure they won't recognize your voice, call them yourself.