I don't mind my partner having sex with other people, but now that we live together, it's hard on me to hear it

Me and my partner have been in a happy open relationship for over 2 years. During this time we have both had other intimate relationships with other people and with other people together. Around 6 months ago we agreed to be primary partners and moved in together (separate rooms). I have no issue with my partner having sex/relationships with other people, however I never realized before we moved in together how difficult this would be to be around first hand. I'm having major difficulty dealing with listening to him having sex in the next room as it makes me feel insecure and upset. I understand that he needs the freedom to have his dates in his own room but I’m really struggling knowing what is happening in the next room and being able to hear. It’s not an option to move out. How can I process this so I am able to give my partner the freedom that he needs like he is able to give to me?

If the issue is really having to be around it and hearing it and generally being actively aware of it, the solution is relatively simple - some noise canceling headphones, or asking for him to give you a heads up about planned dates so you can hang out somewhere else. It might be time to find a local cafe you enjoy hanging out at, or some close friends who are okay with you setting up on their couch some evenings. You can also talk with him about this, let him know that it makes you feel insecure and upset, and ask if he can maybe come up with some compromises, like trying to have dates at his partners’ place whenever possible, or monitoring the noise level.

But if you think that, even while you were out of earshot or snuggled up with noise-canceling headphones, you’d still feel uncomfortable knowing that he was somewhere having sex with someone, then that’s a tougher situation to resolve. You say that you have been happily in an open relationship for over 2 years, though, and that you don’t feel bothered by your partner’s other relationships and sex, so hopefully, taking steps to protect yourself from this specific squick-trigger will help.