Swingers stories and erotic fantasies

First let me set the scene, I'm a 42 year old married guy who works in a small office with a 47 year old married part timer who only works mornings. To describe her as plain would be more than fair, thick set and with mousey hair and glasses, I have to admit that I'd never been in any way attracted to Alison, until the fateful day when everything changed.
She came in to the office carrying a sports bag which in itself was a little unusual. She explained that she was meeting some girls for lunch and wanted to have a change of clothes rather than meeting them in her work clothes. Lunchtime came and after changing in to her jeans and tee shirt she said Bye and see you later. Left on my own with the bag I was drawn to check it's contents imagining that all I'd find was the skirt and top she'd been wearing all morning. My hand delved in and Oh My God what was that sensual satiny feel, it was, it was her knickers still slightly warm and smelly. Straight away I put them in my pocket and made my way to the Gents toilet. Trembling with excitement I got naked and slowly pulled up them on. How good did that feel? the smoothness of the material and the knowledge that my cock was rubbing against a piece of cloth previously pressed against her hairy snatch. As I stood there lost in my own little world or rapture, disaster struck. Without any warning I came powerfully and messily, I couldn't bring myself to whip them off, but who would? Instead I watched as the light green material developed a dark green patch around my twitching cock.
Now came the panic, what the hell do I do? I washed the sticky cum off as best as I could and stuck them back in the bag, maybe she wouldn't notice and just stick them in the washing.
My answer came at lunchtime the next day. 'I think we need to talk' these words struck me like a knife, 'Did you cum in my green panties yesterday?' What the hell could I say? I nodded and mouthed the word yes. 'Come with me' I followed her to the Ladies, 'take your trousers off'. Again I did as I was told, slowly she started to rub my cock through my pants. As I said she's not attractive but the whole situation made my cock as hard as iron. 'Lets see what your wife says when you get home'. She rubbed harder and faster, not with any great technique if I'm honest. But eventually it happened, once again my pants were soaked as my cock pumped cum. To be fair she didn't stop immediately but made sure I was totally spent before making me put my trousers back on.
I had thought that eveything would be back to normal, once I had managed to ditch my pants before my wife caught me but how wrong I was.