He Is Still Fucking Her

Following on from my previous message…

My is 28 yo and has been made pregnant by a 15 yo boy.
He doesn’t want to know about it.
She doesn’t want to get rid of it.
Should I pretend that it is mine… not sure what to do.
I am 41yo

I came home from work , my wife was not around, heard noises upstairs.
Going up to our bedroom I pushed the door open… I could not believe what saw..
my wife was naked lying on our bed…the 15 year old was just taking his underpants off.
I could see his erection … it was slightly smaller than mine… why would she want that I thought !
I wanted to storm in and confront them… but for some reason I didn’t.
I watched as the boy moved on top of my wife.. her legs opened as he did.
He fumbled about then I saw his arse shove forward.. my wife moaned .. he was up her.
He started thrusting between her legs humping away! I started to get hard… I watched for what seemed ages… but was probably only a minute, then I quietly closed the door, went downstairs and jerked off in the toilet!
I Feel so pathetic and ashamed to admit that I loved seeing them together!
I went for a walk…, when I returned I confronted her and she lied and said he wasn’t there.
But when I told her that I had seen his blue underpants on the floor she broke down and admitted it.
She said it was the last time… it was his 16 birthday so she wanted to please him one last time!
I suppose the only silver lining is that he cannot make her pregnant, because he already has!
Why do I get so turned on by this?