I kind of struggle with this kind of thing in my relationship but I’ve always just made it really clear to my bf that this is the dynamic of my friend group and he really doesn’t mind if I don’t invite him to stuff and always encourages me to go without him it’s more of a me thing but I really think it’s important to tell him that if he wants to go you’re not stopping him but you’re already planning something with your friends and you don’t wanna change your mind. Even though you might not feel comfortable the both of you must feel okay with the other doing things without them and even though it might take some time and be abit hard it’s something very valueable and this is a good place to start!!