Coming to a custody agreement out of court?

My I guess now ex fiancé are separating and I’m trying to figure out how to come to a coparenting agreement without involving lawyers but he’s being so stubborn. My son is 7 months and still breastfeeding so he needs to be with me the majority of the time. I’m also on maternity leave for another 5 months...

He works weekends so I’m thinking maybe he has him 2 days a week and I have him the other days? Maybe 3 days for me, 1 for him, 2 for me, 1 for him?

I can’t be away from my baby for multiple nights in a row but also don’t want him going 5 days without seeing his dad...

Any advice would be helpful.