So wrong, but feels so good

I can't believe what I did last night. I was sitting on the couch looking at a magazine when my step-son surprised me by coming home early. He was obviously upset and so of course I wanted to comfort him. But I notice he is staring at my boobs which are practically falling out of my top. I attempt to cover up but he insists that seeing them will make him feel better. After all I am his stepmother and that is just wrong. But he persists so I take off my shirt and expose my big beautiful breasts to my step-son. Then in turn he exposes himself to me and oh my goodness I had no idea how big and hard his cock was going to be. I am so ashamed to admit that I was instantly turned on. I could feel my pussy getting wet. Somehow he convinces me to masturbate for him and then one thing leads to another and we end up in my bed with me on top of him riding his cock. How could I do such a thing? How will I face him this morning? And will it happen again?