Baby is sick and ex didn't even tell me

So my ex and I go back and forth on weeks with our 8 month old and my ex brought our son back and I noticed he had diarrhea like water and then he acted like he didn't want to eat and threw up so I asked my ex how long he's had diarrhea and he said since yesterday and I asked him why he didn't tell me that our son was sick and he's like he just has diarrhea and I'm like he threw up as well and my ex is like yeah he probably has what we all had this week and I'm like why didn't you tell me he was sick and he said you don't tell me anything so why would I tell you anything.. I don't talk to my ex unless I absolutely have to and when I do it's only about our son. I would definitely tell him if our son was sick or if anyone else in the house was sick just in case.. I have 2 other children at home and I work full time so getting sick would suck especially since I had to use all my pto on a car accident I had last month.. I am upset he didn't let me know our son was sick and he acts like it's not a big deal and I should get over it. Am I overreacting? I don't know what they had and I don't know what my baby has.. If he would have told me I would have asked him to keep him a few more days. Like who does that!? Also I wonder why he wouldn't ask me to come get him if he knew him and the people he is around are sick?? Why risk your baby getting sick?

Just so everyone knows we don't have a custody agreement through the court's this is just how we decided to do it since he gets his other children the same days of the week.