defamation/slander

What are my rights? I was hired by a local LTC facility as a RN. During the paperwork orientation, I was told after the 3 hour break that they would not be able to hire me because I had a bad reference. They will not tell me what was said or who said it. I believe the information being provided is false and malicious. I have only worked in two places. Another local LTC and the VA hospital. Both claim they only give out date of employment. The professional references came from the local LTC. Four professional refs were asked for. I know that 3 of the 4 did not say anything derogatory however, I am not sure about the DON. The LTC faught against paying my unemployment and the DON was basically caught in a white lie. I have been unemployed for over 6 months and feel this bad reference is the cause of my continued unemployment. The reason I was let go by the 1st LTC was due to low census. They tried to say I quit because they didn't want to pay my unemployment.
I would pay for a consultation if I had the money but I only receive $800 SSA (death benefit). I am a widow who has a mortgage, utilities, and child to care for. I have also been force to accept medicaid for the both of us and I am waiting on approval for foodstamps.
I would appreciate any information you can supply and thank you for your time.

Sincerely
kathy