AITA for being uncomfortable when my 7-year relationship turned into a thruple with my best friend?

i (22f) have been in a relationship with my bf (22m) since we were 14. i met this girl (19f) at my job, and we quickly became friends. we’ll call her madison. my bf tends to get involved in all of my friendships, which i never minded. we all kind of became like a little friend group and hung out a lot. madison would talk a lot about her conquests (lots of one night stands, threesomes) but at the time she was in an abusive relationship. it got to the point where my boyfriend and i even moved her out of her then boyfriends house when they broke up. my boyfriend and i were pretty vanilla but had talked before about having a threesome but it would have to be the right person. i was comfortable with madison, and my boyfriend was definitely on board. madison had expressed interest in us before, and when i brought it up she was all for it. we talked some rules beforehand, and ended up having a threesome. afterwards, we smoked and talked and everything seemed fine. the next day- neither of us heard from her or any of the friend group so i decided to drive over to the house everyone was staying at to see what was going on, as i had previously had an open invitation. i arrived only to find them all talking about how i was a terrible person and a manipulator. so confused, i announced myself and asked what was going on, apologizing if i had overstepped in any way. my boyfriend had suggested “trying again” so we can make it “better” this time. i was at the point where id do anything to save our friendship so i agreed and so did she. it went great again, and we make the effort to make sure there was aftercare. after that, it seemed to just keep happening. she was also sleeping with multiple other people during this time as well. as time went on, my boyfriend started treating her as if she was also his girlfriend, and encouraged me to do the same. he would always say “well you love her don’t you?” which is a really hard question for me as i am autistic and really did love her, as a friend. but the sex was fun, when i was involved. i’d wake up in the middle of the night to them having sex right next to me. if we were all watching a movie and i left to use the restroom, id come back to them having sex. it was a daily thing. it honestly got exhausting. when i expressed my concern he would always tell me i just “have to join in” eventually, we somehow became a full blown thruple, and i became increasingly uncomfortable and honestly depressed.but everytime i would bring it up i felt like i was being gaslit. eventually, i had enough and called it off. madison completely stopped talking to me saying she was heartbroken, and my boyfriend became practically catotonic saying he was in love with both of us. he stopped hugging me, kissing me, touching me at all really, and saying i love you. i was so heartbroken and depressed i really didn’t know what else to do but both of them made me out to be the bad guy for “ruining our relationship” even when i got depressed to the point of admitting myself to the hospital, my boyfriend still wouldn’t talk to me or support me in anyway, and he was still talking to madison on snapchat every day even though she wasn’t talking to me, and i can’t see anything that they are saying because it’s snapchat, and i asked him to create space between them so we can work on our relationship and he pretty much refused and continued blaming me for breaking his heart and i held him while he cried in my arms over another woman. am i the asshole?