My wife was in hospital after just having our first baby. I stayed with her until she fell asleep and then made my way home. I was horny as usual and phoned my mistress (calling her Emily) to arrange to pick her up on the way. Emily and I had been having an affair for a few years and used any opportunity to get together for sex. I collected Emily and drove to my house where we immediately retired to the bedroom for a fucking session. It wasn’t long before we were naked and enjoying each others body. I love panty swapping so I had Emily wear a pink cotton panties belonging to my wife. (I love fucking a woman while she is wearing another woman’s panties).
All was going great for a while, we were having our usual amazing (ten times better than the wife) sex. I was on top in the missionary position. Emily was gasping and groaning underneath me; her fingers were dug into my ass plunging me deep inside her as she pleasured herself on my prick. I knew she was about to cum and I was more than ready to join her. Emily’s body began to shudder and she soon began her usual gasping with “fuck me, I’m your whore” dirty talk. I replied calling her a slut and a bitch for fucking her friend’s husband while she was wearing her friend’s knickers. The dirty talk pushed us to the edge and brought a loud gasp of pleasure from Emily. I knew she was “on the brink” as I felt her pussy clamp onto my prick. I felt my own raw lust build up and I was ready to shoot my load. I stroked faster and then felt the wondrous sensation of my cum shooting through my throbbing prick into Emily’s pussy. Emily’s orgasm was almost instantaneous. She jerked her hips towards me and began to cry out loud coming hard and shuddering all over.
All I could think about was shoving my cock into her wet, tight pussy and filling it up with my cum. I was well past the point of no return when suddenly a light shone in from outside through the half open door. The room became illuminated in bright light. My immediate thought was “my wife has come home”. I watched in horror as the door fully opened and, as if in slow motion I saw, not my wife, but my wife’s older sister poke her head inside. I could only stare at her as her expression changed from mildly curious to bad surprise and then just pure raw horror.
The sight that greeted her was one of confusion and naked bodies. The bed covers had long been kicked off so we were fully exposed when that light came on. I was desperately trying to withdraw from Emily’s pussy even as my prick was still ejaculating my load. Emily was in the process of screaming out her first loud “ahhhhhhhhhhhh” while turning her head towards the door to see our unexpected visitor. My brain felt on fire as contradicting commands were issued that my body and dick were in no position to carry out. I just could not stop coming. Emily was looking towards Mary but her gasping continued and I knew that she was also having trouble in stopping. She no longer screamed but couldn’t help whimpering quietly as her body continued to orgasm
Pulling out my dick at that point wasn’t a very good idea. I should probably have stayed inside her until I had finished. As it is I finally withdrew my still pumping and throbbing cock only to make matters worse by involuntary ejaculating the remainder of my cum into the air. I tried to stop it with my hand but I think that made things worse. I looked at Mary; her expression was showing pure and utter disgust. Her face was deathly white and she looked close to fainting. I saw her start to gag and then she suddenly turned and left.
I heard her run to the bathroom where she proceeded to throw up. We got dressed quickly and made our way to the car. Even as we crept down the stairs we could hear Mary retching in the bathroom. I drove Emily home. We were both pretty shaken and wondered what Mary would do after catching us. I arrived home about a half hour later. The house was quite with no lights on so I made my way to bed. The next morning I was woken by the sounds of conversation. I immediately recognised the voice of my mother in law speaking to Mary. I guessed by now that they had arrived a day early. They had a key and must have let themselves in the previous night and went straight to bed in the guest room. Mary must have been woken by the noise of us having sex and came in to check things out.
I showered and eventually made my way down to join them. My mother in law was her usual cheery self so I guessed that Mary hadn’t told her anything. Mary herself was like a different person, where as normally, she would be chatty and outgoing, now she was withdrawn and sullen. Her body language screamed “stay away from me you sick fuck”. She barely spoke to me during breakfast and I’m sure my MIL was suspicious. After breakfast, I drove them to the hospital for a visit. The visit was pretty uncomfortable so I made an excuse and left. When I returned later, my wife was alone. She told me that Mary wasn’t feeling well so they had returned home early, deciding not to stay the second night. My wife was pretty pissed at them for leaving early and blamed it on Mary saying she was jealous because she had been trying without success to have kids herself.
I stayed at the hospital until she fell asleep and then left to call Emily. I picked Emily up on my way home. My wife would be home the following day so we wanted to make the most of the night. This time we checked all the rooms and put a lock on the front door before we hit the bed. Once we settled down we spoke about what had happened.
Emily said that she found getting caught was extremely erotic and it made her really horny just thinking about it. She said that at first, when she had seen Mary she had almost had a heart attack. She had felt extremely embarrassed to be caught naked on her sister’s bed. But after I dropped her home, she began to relax. She thought back to what had just happened and she felt herself getting wet. She said the memory of Mary standing there, watching her being fucked was a massive turn on. She had gone straight to bed (still wearing my wife’s undies) and masturbated herself to sleep while remembering how she had just orgasmed in front of my wife’s sister.
That night the sex was incredible as we both gorged ourselves on each others bodies along with the memory of my sister in law watching us.

This incident happened a few years ago. As far as I know Mary has never told anyone in the family. She is still quite sullen in my presence and we rarely speak. This isn’t an issue for me as we live in different counties so rarely see each other. It isn’t the only time that I was almost caught cheating but it is one of the more memorable.

I should mention that I am a serial cheater and sex addict. I have some pretty mild but weird fantasies that I make it my business to act out whenever possible. Most of these are carried out with my mistress but I stray even from her quite often (I tell her about some of my straying, but not all). I love women and will basically hump almost anything in a skirt. I use call girls when I am abroad if I don’t “get lucky” with a local woman. I have a collection of used panties hidden in work that date back about ten years (yes I do have to occasionally wash them or they get hard in the crotch). Each of the panties has a special significance to me. I bring out various panties with me every time I’m with a woman. I almost always have sex with women (inc my wife) while they are wearing another woman’s used panties. Then I usually talk (or buy) my way into keeping the panties that they arrived wearing. My favourite type is the small (not thongs) cotton briefs, either plain or with shapes. The more women I get to wear the same panties, the more I value the panty.

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