At the time myself iain 22 and my gf Jen 20 had just brought our first house. I was in the Army and my gf was an estate agent we had some close friends Claire and Mark both in their 20s they used to stay at ours on a weekend while the looked for their own place and we had some parties. When it happened I was coming home on leave on the friday and I was bringing a mate from the army as we was going to a football match on the Saturday. We got to my house my gf and claire ws still at work so myself and chris my mate from the army decided to go to the pub.. After a few beers I got a messageof Jen saying her Claire and Mark was at home and was wondering where we was so i said come to the pub we have few drinks and dinner there.. We didn't leave the pub till closing time all of us was a bit pissed but carried on Drinking at home it got to about 2am and I started to doze on the sofa so I said I good nights and went to bed and Jen said she be up after her drink. I woke up some time later needing a piss and noticed Jen wasn't there but I could hear Claire and Mark both having sex and her moans was turning me on. I quickly went to the toilet then went to see where Jen was as I got to the top of the stairs I heard Jen giggling so creaped down a few stairs as they led straight in to the lounge and through the gap in the rails I could see Jen and chris on the sofa kissing and playing with each other. I froze my heart was beating hard my stomach was in knots I was angy and jealous but also turned on horny.. i never really discussed anything like this with jen but it was happening and all i could do was watch. Jen was a size 10 with 36 dd boobs and a nice trimmed pussy. I could see chris working his hand into Jen's jeans and was fingering her she was also working his cock out of his jeans. Next I see her lean over and start sucking his cock he had an average size penis like me about 8 inches at this point I was hard as rock and I was slowly stroking as I watched her head was going up and down. She suddenly stopped and said they needed to stop as she didnt want to cheat on me then chris suddenly moved his hand deeper and i heard jen let out a long low moan and give him a deep passionate kiss she move her hips up and he pulled down her jeans and thong in one move. She then straddled his cock and I could make out that he was rubbing it against her pussy she stopped again and moved off his cock saying they can't cause they need a condom. He said he didn'thave one and the ones we used was in our room. I thought that would be it she wouldn't do it she wouldn'teven let me near her pussy without one then to my surprise she grabbed his cock and slipped straightin her she just said to him don't cum in her she started to ride him kissing deeply and both was moaning as she was picking up the pace. Then I felt a hand on my shoulder and it made me jump it was claire she had seen me watching. We snuck back to my room she said mark has passed out she was just in a vest top and pj shorts. She wanted to know what I was thinking and doing I told her how I felt and that I didn't know what to do but I said to her that I didn't want Jen to know that i knew . Claire went back to bed and I went to watch again as she walked off I noticed a wet patch where marks cum was leaking out. When I sat on the stairs again I noticed they had moved from the sofa to the floor and chris was pounding her hard in the missionary position jen was moaning quite loud now telling him " fuck me harder" "deeper don't stop" just keep going.. they was kissing more passonaite Chris slowed down and said he was cumming just as Jen was reaching an orgasm she told him don't stop she wrappedher legs round him and pulled him in close while moaning and kissing him, he let out a final grunt as he emptied his spunk into her unprotected womb they lay there kissing and I snuck back to bed with cum on my boxers.. I heard Jen come up and go to the toilet then climb in to bed with me I pretended to be a sleep and rolled over and cuddled her we moved in a spooning position and I slipped my hand down to her pussy she tried to stop me but I my I worked cock in from behind. She the rolled on to her back and I climbed on top and slipped straight in to her cum filled pussy it felt really wet and hot and it turned me on so much I cum in 5 minutes she never said anything about a condom or me cumming in her then we both went to sleep.. We was woken up by Claire and Mark fucking again and I climb back on Jen and slipped straight back in and again she said nothing about protection. We got up and went down stairs chris was outside having a fag and I went out and join him trying to act normal Jen started making the tea when Claire came down she asked me if I was ok and I said I was good I enjoyed it but still keep quiet soon after me Chris and Mark left for the football.. Part 2 soon