Looking for this story

As in the title I'm looking for this Story. I read it a long time ago and it is driving me insane literally that I can't find it. I believe that it is from http://www.literotica.com/. Okay so I will describe it the best that I can.

1)It involve a mother and son.(Or a relationship along that lines, Mother figure taking care of only child male)

2)It is from the view of the mother.

3)the Son is small for his age. I mean he looks younger then he actually is.

4)the Father is out of the picture.

5)there is a scene where she masturbates with a dildo, on the phone. the son watches (thinking the mom can't see her, but she does know and that is why she is masturbating)

6)Near the end, she does him in the ass either with the dildo she masturbated with or a strapon. I believe it was the dildo becouse I remember her thinking that she should get a strapon to do him.