My Weekly Exercise With My Son

10 years ago I married a man who at that time had a 7 year old son.
He mostly lived with his mother and stayed some weekends with us.
About 6 months ago I accidentally walked in on him in the shower. His cock was so big I cannot believe he is his dad's son. Easily 6-7 inches soft dangling there!
So I set him up a day later showering and forgetting a towel. I yelled for him to get me one and walked out of the shower naked. I am slim with perky boobs.
His mouth fell open and he looked up and down. I walked up and gave him a hug and I felt his third leg jump. I thenslowly went to my knees, and undid his pants. He was so hard now and I have never seen anything that big! it was easily 9 inches and so thick that I needed two hands to reach around it! I started sucking him off. He exploded very fast, but being 17 years old, he stayed hard, so I bent over and opened up! He almost ran up and tried to force it in, but it was so big that it didn't fit, so I turned around and sucked him again.
After this, we have planned playing "tennis" together every Tuesay and Thursday and some weekend days, and he fucks the living shit out of me. The first time he entered my pussy I had an orgasm right away. In that second!
It feels like an arm thrusts inside of me!
He is soon going off to college, and I know he will surprise a lot of girls. Especially since, I have taught him how to eat pussy now also. So now he eats pussy like a pro and fucks like a pornstar for hours without breaks!
I hope we can continue to play tennis in the future. Maybe I need to offer him my asshole, but I am unsure how gaped out I would be