My question involves paternity law for the State of: tennessee

My husband and I have been separated for over two years but no legal divorce has taken place. We have three children together. I recently had a baby by another man. This man denies the baby now. For the first four months of the pregnancy he was involved. As soon as we found out the child was a girl he said it was not his. From then own he along with his new fiance have badmouthed me and my child. I usually can not take my baby out of the house without and incident occuring. All I have asked is to be left alone by both of them. That has not happened and I doubt it will. I am tired of it all and want to know what I can do and what the biological fathers rights are. My husband was named her legal father on her birth certificate because we were not divorced. What can I do?