It is the most horrible feeling when a child who loved DC becomes distressed at drop off time.

DD1 started hating DC drop off when I was about 24 weeks pregnant and it would break my heart every time. DD1 went on Wed & Fri but I had changed her to a one off Monday when I was booked for 41weeks monitering, I had DD2 very early on a Sunday morning the day before and I was home that afternoon. I took DD1 to DC the next day and she was prefectly fine. Back to her usual happy, quick kiss and a wave while she runs off to find something to play with. I think she new there was a big change coming but not sure what. When she could see DD2 I think she understood and was then fine.

Sorry for the long winded story but it might be similar for you. I hope that he settles again soon for you.