Mommy Can't Stop Her Horny Son

I was just innocently searching through my wardrobe for something to change into when my son pushes me forward. In hindsight it was my own fault for wearing such revealing shorts like that around the house.. it was only a matter of time before his raging hormones would get the better of him, I was surprised he'd held up his self control for this long without doing something inappropriate! Suddenly he pulled my shorts right down and just.. stuck himself inside of me! I didn't even have a second to react. I tried to encourage him to pull out.. that Mommy isn't on birth control but he just kept on fucking me until I was pumped full of his cum! I turned to him, confused and embarrassed at what had just happened, panicking about the possibility I could be pregnant and try to leave to take a shower, but he reassures me that maybe having sex a second time would help ease the cum back out of my pussy.. of course I trust he's right so I dutifully sit on his rock hard dick until he cums again. Something wasn't quite right about this.. surely this would actually up my chances of getting pregnant not lower them?! He informs me that I'm now his free-use mommy and that we can keep it a secret from his dad.