Boss Asking Me To Extend Pumping Frequency At Work: Illinois

Pretty much what it says. I’m a nurse and work in a busy clinic. My job will include case managing soon for an assigned doctor several times per month. Right now I pump every 3hrs as it mirrors somewhat closely to how my baby nurses which is every 2hrs. My boss in asking me to extend the length of time by several hours on days I case manage, up to 5 or more hours. I’m pushing back on this. As far as I’m aware this is illegal? I also physically can’t go 5 hours in between pumping because it gets super uncomfortable and will leak, etc. Lastly, I don’t want an employer having say over my bodily autonomy because of their “business needs”. It full on gives me the ick. Any advice is helpful, I’ve read both the federal & Illinois law on this and trying to figure out how to navigate this.