Presumption of Paternity: Hospital Made Me Put Ex Husband on Birth Certificate

My question involves paternity law for the State of:
Mississippi

My son was born in Biloxi MS, I was still legally married to my ex husband at the time of his birth. The hospital made me put my "husband" at the times name on the birth certificate instead of the real father. They say I need a court ordered paternity test to change the father's name on his birth certificate, but I'm not sure how to obtain that. I have got my divorce and the decree, and they still will not let me take my ex husbands name off and put the real father on. Please help

Presumption of Paternity: Hospital Made Me Put Ex Husband on Birth Certificate