My partner of 4 years went away for a week on a family visit. Whilst on this visit, a family get together was arranged at the parents house. Included in the family get together was the ex who by all accounts is still friendly with the parents. To cut a long story short, my partner and ex, ended up sleeping in the same bedroom and in the same double bed that night despite the ex having another room prepared. I was not informed of any of this and only found out when I had suspicions. I was first told that they slept in separate rooms. My suspicions and paranoia knew that there was something more to this and I snooped in on a conversation they had been having on a chat site for quite some time which alarmed me. I was enraged with jealosy and hurt and at 4 in the morning texted the ex from my partners phone " M knows we slept together" The response was " "who has said something?" The next day I confronted my partner who then admitted that they had indeed slept together but were fully clothed. My partner also said that they went to bed in separate rooms but my partner awoke in the morning to find the ex asleep in the bed as well.needless to say a lot of alcohol had been consumed. I have been told that nothing happened and I have to believe that it didnt for my own sanity. On a break, about a year ago, they actually did sleep together. My mind is going crazy and I am struggling to deal with it. I need good strong advice apart from LTB which I guess will be the stock response.