[MI] Do I need a lawyer to fight for full custody?

Just for some backstory - Me and my ex have a child together and we’ve been “successfully” coparenting since the child was born. Child is 3 now and in January the other parent called CPS on me with false allegations even using my partners social media posts as evidence despite the child not even being in their care and filed for full custody. The other parent filed for full custody and hired a lawyer but we ended up getting it moved to the Friend of Court and now I have the child Sunday-Thursday while the other parent picks the child up Midday on Thursday. The other parent’s partner is constantly overstepping their boundaries and trying to take full control as if she was the child’s mother. So my question is do I need a lawyer to fight for full custody or can I gather as much evidence and fight for full custody. Ideally I’d just like for the other parent to get the child every other weekend.