Is there such a thing as too much pretending in a 5 yr old?

That ok! She using her imagination! That great. And cute! While my aunt her little girl is 5 too. She alway says she is pregnant and like to play by herself. Had an imaginary friend name Kayla one day Kayla would be 39 the next day Kayla is in 5th grade the next day she 2. It because she had an old sister who was always at school so she has to get creative and make her own friends! It probably cause Your son is so young she doesn't have someone to play with!