How do we work this out?

Me and my ex have been apart for a little over 3 years now and we have almost a 4 year old. He starts school next year. Now he is a great dad and we have been co parenting since we split. Due to school starting we gotta figure some things out. He moved an hour away about a year ago and we currently do week to week with our son. But with school we have no idea what to do. Neither of us only want him on weekends and not weekdays. We cant decide how to go about this. It seems like one of us has to cave but im not sure who. Again im not bashing him, hes a very good dad and a good person. This is just a hard decision in co parenting. Do i let his dad have him for the week for school by him? Do i take a stand and say hes staying by me for school? Im also pregnant with my current fiance if that makes any difference. I just know id miss my son so much