bunking with your horny pregnant stepSISTER

I arrive back at my family home after my boyfriend broke up with me leaving me pregnant and with nowhere to stay. Unfortunately, step-mom has turned my old bedroom into a private yoga room and makes me share a bed with my step-brother, just until we can figure something out. I ask if he'll stay on the sofa, but nope.. he likes to make my life difficult (obviously!) .. I get unchanged and into my pjamas whilst he's in bed and promises not to look. In hindsight I should have got changed in the bathroom, but he's my step-brother.. he wouldn't think of his step-sister in THAT way, right? Anyway, we lay in bed and chat for a moment and I feel it's only right if he knows that lately I've been waking up in the night masturbating and I can't help it.. its just a side effect of me being pregnant and extremely horny with no boyfriend to satisfy me and he promises that he won't get weird about it if I do. I turn over from him and close my eyes.. and thats when I wake up a few hours later with my hand reached around and grabbing at his cock, jerking him off! I didn't even MEAN to, I wasn't even awake! I apologise to him.. but he doesn't even seem in the slightest bit annoyed.. in fact, I think it actually made him horny for me.. his own step-sister! I try to brush it off but he puts his hand in between my legs and starts to play with me.. I try to stop him but it just feels too good.. its JUST what I need right now to take my mind off the heart-break. I push him away and protest that he NEEDS to stop right now because I'm going to cum.. he stops and looks at me.. smiles like he knows how to make everything better and climbs on top of me, using his body to spread my legs apart.. I tell him we can't.. its taboo.. I'm pregnant.. its so many levels of wrong, but we both aren't strong enough to fight our urges and he pushes himself inside of me, filling me up with his thick length. I moan in pleasure as he fucks me slowly at first and gets harder.. deeper.. and then I get on top and ride him until I've milked all the cum from his cock. We then lay down next to each other and kiss.. I tell him that this is our secret.. our taboo secret forever.