30M here been with 31F for over a year. We love like 2 cities apart but i visite every weekend normally sonce we both get weekends off. Shes bi and okay with polyamorous situations.(im not so okay with it). (One of her fantasies is to have a 3some with 2 guys. This plays a part later) So she has a best friend, male, thats she’s known for several years but lives in a city on the other side of the state. Hes bi, married and in a polly situation with several partners. She assured me they were just friends and nothing would ever happen unless she talked to me about it first. I even dog sat while she went to his wedding. Well couple of months ago he was heading to her city to visit one of his partners and she said he could stay with her first the week while hes visiting. She asked me if i was okay with it first and assured me again they were just friends so i was eventually okay with it, though hesitantly. Then before he was supposed to visit she revealed that they had a BDSM sorta friendship where she liked to be tied and spanked/whipped but never went beyond that. So again i was a little hesitant but also understanding because i don’t like inflicting pain on people. Then she said he wanted her to make him deep throat a strap on, and again promised/assured that it would not go beyond that, no sex. That week passes and she said they had fun driving around and that nothing happened. Then recently he was visiting again and she again promised nothing would happen and no bdsm stuff between them this time. And id would be seeing her over the weekend and meet him. She said hed sleep in the living room. The night he arrived to see her i was still home working and usually she’s constantly texting me after work and before bed but this time she didn’t text me at all till the morning. I was a little worried but didn’t think anything about it. She said they just stayed up all night talking about me. Fast forward to me arriving at night and they have another friend over (female) and all playing Mario party. I get there and shes immediately all over me and physically more affectionate than usual. Even pulls me in the kitchen and asks me to leave marks,hickys, on her which isn’t normal for her. After the female friend leaves and all ready for bed he askes if it’s okay for him to sleep in the room on the floor despite being informed he’d sleep in the living room. I said id be okay with it because we were supposedly just going to sleep. Then he stated he sleps in his boxers. We are all laying down and lights out and that’s when my gf starts cuddling but in a way that she’s rubbing on me with her hands over my pj pants and very intimately, which again she has never done and isn’t normal. When my body reacted she seemed excited and was like “oh you want it” and moved my hand to her panties. After some rubbing she asked if it was okay if she sucked her friend while i was inside her from behind. It caught me off guard but i knew it was something she’s really wanted to do so i said okay. Se she immediately sits up and says “want me to suck your dick” and he said okay and it all seemed too easy and normal but i tried not to think about it. I could not get hard because i felt very uncomfortable and then felt guilty i couldn’t get it up so we switched positions and she sucked me while he was in her. When i was hard she wanted to switch back and again when i tried to enter i got soft again. He came and she said she wanted to finish me off so he went back to the floor. She sucked me and rode me till i finished. I thought it was all over but while cleaning he asked her to get her water and while in the kitchen he asked me it it was okay to steal her for a little. I didn’t really know how to answer so I said it was up to her and of course she was more than happy to do that so I was laying down in bed and her dog was cuddling while they were on the floor doing there thing. Was loud and lasted a very long time. Was uncomfortable and pretended to sleep the whole time. They eventually finished and went to bed. In the morning she walked her dog and came back and went to cuddle him on the floor, which she doesn’t do with me. We all wake up to do errands and go eat breakfast and when getting ready he says he want to leave a mark on her on the other side of her chest, i made one one her that night, and she said no she was still mad for the one he already left on her the previous night. That comment caught me off guard and when i looked closer she wad a mark on her neck and cheek already where there was a bandage previously when i had arrived. I didn’t bring it back up because i didn’t really know what to say. Weekend goes by and he continues to be very physically affectionate with her and i felt like a third wheel. When he finally left my gf and i finally had a conversation and i finally asked what happened the night before i arrived. She finally admitted they did in fact have sex and she said she initiated and that was why she had asked for me to leave a mark on her. I was upset and she asked if that was the end of us and i said no because i do love her and she said she loves me and it would never happen again and there will be more strict boundaries between them. Even start a group chat “so we are all on the same page” i asked if they did anything like that last time he visited and she promised absolutely nothing like that happened last time. During my work week i was still bothered by it and a friend advised me to have further discussion with her. It was during this discussion it was revealed that she had lied and they did infact have full on sex last time he visited too. I was further hurt and she said she didn’t want to say anything because she didn’t want to hurt me or it to affect my work week. It hurt more i think that she hid it and I literally had to like be a detective and ask her myself. It’s been a couple months(i think) since then and i want to get over it because i do love her and she’s treated me better than anyone ever has and i don’t want to leave her but i can’t stop having negative thoughts and being paranoid about what she’s doing throughout her week or when i can’t visit a weekend. How do i get over it? Should i be upset or am i wrong to be upset? Was it cheating or was it not cheating since when we got together she told me if i ever met anyone then i could date others while with her,even though i told her i wouldn’t and dont want to. (My past relationships i was cheated on in similar situations where i ended up finding out but they left me for them) shes the first person ive felt so strongly for but i don’t know what to do or how i should feel. (To add further context as to why i would be okay with opposite sex staying with her and believing nothing would happen is because im roommates with my high school/only friend who is Female and we’ve never crossed that boundary or even considered it so I figured it might be a common situation that occurs)