Separation

I have worked full time all of J's life. Being a teacher, I am lucky to have off all holidays and so it is an ideal job to have when having a child. To top it off, Paul and I have a schedule where J is in very minimal daycare so he is usually home with one of us. So I have had off about 2 weeks before Summer school started. There were a few occasions in those 2 weeks where my m-in-law watched J for a few hours, which happens frequently, as she watched him one afternoon per week during the school year. Well, all of a sudden, J is crazy about being home without me or Paul. He is so worried about going to daycare, or having someone else watch him. It is weird. The only thing I can figure is that I was home for over 2 weeks and he just got super-used to me being home and he hates to see me go. I told him today that I have to work tomorrow and he was crazy asking questions....Who was coming over? Did mom-mom have to come? I explained that I will be home before dad goes to work and that I am only working 1/2 day. But he keeps asking questions. I am sort-of glad to go back to work so J gets used to "real-life". I didn't think kids at his age got like this but here we are! Anyone with a 4 year old, have you dealt with this?