7 year old step son is playing with feces

[Stirk]

My 7 year step son has been playing with his fecal matter whilst on the toilet he gets it on the walls, floor, toilet, & himself.but the most disturbing thing for both his mother and I is that we have both discovered him playing with his feces with an erect penis, this has caused us to wonder if there's a possibility that he has been interfered with sexually?

[allmymarbles]

Given that he is seven years old, I would be more concerned that he had developmental delays. It is unusual for a child that age to play with feces. You might want to think about getting an expert consult.

[Sandman2]

It's probably because he has a full bladder.  Very common to be erect when you have to pee.
  Sounds like he is on the toilet a long time.  Is he constipated ?