Custody ???

Jessica • I am 20 years old I am a stay at home mom and a student I have a wonderful little boy and a amazing fiancé
I had a baby January of 2014 his dad has never been in his life about 10 months ago I met the man of my dreams he loves my son and I so much my son even calls him dada 
My sons real father has nothing to do with him only seen him 3-4 times since he was born he doesn't want my now fiancé being in my sons life and he is now trying to get full custody of my son I'm only 20 and I'm so scared has any other mothers went through this