Step Father

My step father caught me masturbating on the sofa three weeks ago, and since then I cannot stop thinking about him and wanting him to fuck me.
I say this because he didn't hide the fact he'd become erect watching me, before I noticed him stood there.
When I did notice him, I was orgasming and couldn't stop. He very casually took out his cock, stroked it a few times and asked me if I wanted him to fuck me.
Just then his phone rang with my mums tune playing on his phone.
Still playing with his cock only feet away from where I lay, he spoke to my mum.
It was clear she wanted him to pick her up, but in my mind I was thinking 'No, I so want your dick first'.
It didn't happen, but before he turned to walk away, he said "Next time hey".
It all happened so quickly I didn't really have time to process what had just happened between us, but once he'd gone I couldn't help myself and masturbated some more thinking about his gorgeous looking cock.
We've flirted like crazy since, but because of college and him working, plus having mum around, we haven't had the occasion to have sex.
The thing is my mum is attending a concert with her friend shortly leaving myself and T at home on our own.
I've already asked him of he'd like to fuck then. He responded by briefly slipping his hand up my short skirt and feeling my pussy through my knickers. When he turned to go into the bathroom I saw a huge bulge in his shorts. And I'm sure I heard him wanking in there too.
I can't wait until next weekend.