SO divorce

My fiance has been separated from his wife for well over a year bow and they have a handsome son together, they are civil and such but he filled out divorce papers and she threw them away, got a lawyer and filed new papers. She wants to keep her state assistance and it pissed me off that she's screwing him like that. Here's the catch, they both get him every four days. He pays child support and she also had tanf and snap. She did all this because she wants the free help. Well, we got her copies of the papers She turned in and it said she was wanting full custody. We got a call from her lawyer saying it's supposed to be joint custody. They are very civil with each other. I'm just over 7 weeks pregnant and I'm so stressed over this. I don't know if it's really joint custody or not. We love this boy more than anything. He calls me mamma even.. I just font know how to handle this. I'm 20 years old and this is just so much for me.. any advise? Thanks!

This is me, my fiance and his son Nolan bug. My perfect family, minus our growing bean.