DS is nearly 5. I split up with exP about 4 months ago after discovering he was having an affair. I posted about it at the time - basically I brought an ill DS home from nursery to find exP in bed with a family friend. He left that day and has been living with his parents ever since.
DS has coped well, I think. He sees a lot of exP. Until this week (when he started school) exP collected him from nursery every day and also had him overnight on alternate weekends.
On the day it happened, I told DS that Mummy and Daddy had had a fight (kind of true, I did a lot of shouting!) and Daddy had left. Since then, I've basically said that sometimes grown ups decide not to live together any more. I've tried to describe it as being a different rather than a bad situation, IFKWIM.
DS was a bit upset tonight. He started school on Monday and I think he's just feeling a bit tired and unsettled with things changing (though he seems to be enjoying school!) He was asking again why Daddy doesn't live with us. I said again that's just the way things are now but it felt like a cop out answer. I kind of deflected by saying he'd see Daddy tomorrow and have a sleepover with him at the weekend and he went to sleep in a better mood.
What should I say? Saying that we were fighting and unhappy isn't true - I was happy at least and we didn't fight. It must have been as much of a shock to DS as it was to me. I feel like I need to tell him something but I don't know what...