C.N.
I can say this is a stage, (even though I wouldn't have known it until I read your request). My son did the exact same thing (he was almost 6). I just went back to basics (like when he was going through seperation anxiety around 2) I reasured him he would be ok, and we talked through it. He is perfectly fine now, (he just went to my parents house for 2 weeks and I was the one having a little bit of aniety, lol) it all lasted about 5-6 months. Good luck.