I was falsely accused of violence in the workplace once I filed a sexual harrasement complaint?

I was told by a co worker that I was performing sexual acts on my supervisor to get ahead. I told my supervisor and filed a claim with employer. The co-worker filed a claim against me at the same time for threatening him and other people for years. I never made any threatening statements to anyone ever. Now I am being investigated, and supposedly there are other witnesses claiming over the years they have heard me make threatening statements as well (all lies, because I do not make statements like that) If I am fired do I have a retaliation suit? Also, they will not tell me who my accusers are. my union will not get involved because it is between two union workers