Junk,
Just be glad that he didnt find out about it (sex) at school being felt up during a movie.

I have a 5 year old daughter. The was (rubbed in her private spots) during a movie.

I had to sit down with a 5 year old and have a sex talk.

I could have died. We just told the truth.

Good luck... i have 4 year old boy that im sure is going down a simalar path to your boy.