Are you already living together? This fiancé is not your child's step dad until you are married to said fiancé.
Some people have a big issue with living together before marriage. In that respect, if NO children are involved... I have no problem with it and I lived with my hubby about a year before we married 27 years ago.
HOWEVER, NO child should be in a situation that is not stable and should not be thrown into a new housing situation unless there is a MAJOR commitment with the parent and his/her spouse.. (marriage).
Your fiancé sounds like an a$$ and sounds like he is living with you for one thing only since he could care less about your child. I'd kick him to the door so fast he wouldn't know what hit him. NO ONE treats my child that way.
You do realize that your child is going through hell because he knows there is no way that his dream of mom and dad being together forever is real. He loves you and he loves his dad and now he is forced into a situation where he is expected to love and obey a fiancé who could care less about him and his bio dad is none to happy about the situation as well.
Believe me, your son knows it, and he sees that you have priority of your fiancé over him. Pretty sad.
Why would you continue to consider a life with some person who will not bother to get to know or interact with your child?
I know that divorces happen and children get thrown for a loop. I am one of them. HOWEVER, I am a firm believer that children should be priority of the parents. Some parents worry too much about finding another partner to shack up with and bed each night.
Read your own question and you see the help you need... Focus on your child. This is not all about you. You brought this child into the world, he deserves stability and unconditional love from both parents.
I am not saying never remarry.... just stop focusing on you for the moment and think about your child.
I am appalled that someone would actually stay in a relationship with someone who is that way to their child. Is the sex SO good that you forget that this is not all about you anymore?
I hope this is a fake post and I pray for your little boy.