defamation of character?

After a month I was fired after days of workplace retaliation from my employer for calling him out on serving food that could potentially poison customers. I found a new job and everything was great, all of a sudden my new employer cut me down to 1 shift. I found out today that my previous employer called my new one and told him I was a drug addict. My new employer proceeded to tell all my coworkers that I'm an addict and to keep an eye on me. I have several coworkers tell me this today as I came in to cover another employee. This defamation costs me my job here and another one in town at another restaurant. I need help, I'm losing my house and need to move out of state now. I passed a drug test for another job last week but it's too late to keep my house and stay here in town. Do I have a legit case to sue? I have several witnesses to all this as well as clean u.a.. and I can continue to volunteer clean urine samples if needed