I just cum only from BB

This isn’t the most fantastic fantasy, but is a real one from this week that I thought I’d share.
I’d just given my gf a really sensual blowjob, and she’d had an explosive orgasm. I was just about to resurface to see if she wanted penetrative sex. I was distracted by her flat tummy, which is just starting to show abs. I kissed her tummy and started to move to her hipbone. It’s so sexy how much it sticks out of her tummy, I’d just started tracing my tongue over its sharp bony contour, when BAM! She drove her knee up right into my dangling balls.

I gasped in pain, as her hipbone filled my open mouth. No sooner had my plums dropped back into the sack, she drove her knee up again, this time holding it there, grinding it into my nuts.

I’m instantly hard, and my duck is sliding around on her thigh. She withdraws her knee to knee me again and again for the next couple of mins, it feels amazing.

Still kissing her flat smooth tummy starts to take me to the edge, “can I… can I…” I start to ask, but it was too late. I started shouting thick ropes of cum all over her thigh. She slammed her knee into my balls harder than before, as the orgasm lasted longer than ever . “Good boy!” She giggled

My body was cold and I was shivering lightly with pain and post-orgasm. She scooped me up and held me close, my face nestled in her perfect boobs.

Often after I cum, I’m good to go again after half an hour and generally still horny within the hour, but I was totally drained!