Hostile work enviroment

I wokr for a manufacturing faclity and I am the only female quality control inspector. On many occasions I feel I have been singled out for harrassment.
I have 4 supervisors and when you get your review they all must sign the review. I have documented several occasions were the supervisors have singled me out. They always come up with ways to discredit me and now that I have applied for several other positions in the company, thier recommendtions for me have left me looking like I am incapable of even performing the simplest tasks. I moved to fla from ct and my last job was a quality supervisor, they do not like the fact i have held the same job as them and remind me my "regal resume" has only gotten me a job beneath them.
While I was pregant last year, I was assinged to inspect a job that was not vey safe, and a few of the male inspectors refused to do the job. I was told even by my mananger I was to go to this work area. I got so upset about having ot do this job, while I was pregant my doctor even put me on Zoloff.
My question is.......what is hostile work enviroment? Am I working in one?
What can I do about it? The area I live in does not have many companys at all to work at and i can not seem to even move up in this company since they are always trying to discredit me. When I first started in this company the HR person told me she had gotten some of the best refrences ever for someone from thier previous employer. Now with this company I am on the bottom of thier list and can not even do the simplest of jobs. I am the only inspector that can not go to the bathroom ( while inspecting a ceetain job) according to 2 of the supervisors, but the male inspectors can go.
I'd just like to know where i can go with this and what can be done. I'm at the end of my rope and about to quit.
Thank you