I have worked 4 years in a doctor's office where my office manager disliked me and harassed me. After I went to the HR Dept for help to resolve this, they turned their backs on me. After 12 weeks of medical leave, I resigned. I have sent out over 30 resumes and do not hear from anyone to interview me. I am afraid I am being black balled. I do not know what to do!

One thing you can explain on your job application where it asks for work references your side of why they might give you a bad reference. Some applications ask may we contact this job? You could explain there why they had a problem with you giving them your side of the story briefly.

The jobs that I apply for usually request a resume sent online. There isn't a spot to explain my situation. Should I put it in a cover letter?

Hi, DowninLuck,
Wow, What about mentioning it in the JOB DISCRIPTION, OR WHY DID YOU LEAVE YOUR JOB. I think they still ask those questions on the applications on line.
Keep trying, allot of people out of work, and give references of people that did like you at your job there.