So me (28F) and my boyfriend (36M) have been in an open, long distance relationship for almost a year now, but our relationship spans over 2 years. Everything has gone pretty well and our relationship mostly consists of us having casual, physical encounters with other people and sharing our experiences with each other. I have been participating more than him recently, but I have no issue with him hooking up with people, especially since he travels a lot for work.

However, this morning, I came across a popular polyamorous instagram person that he follows and it seems like he engages quite a bit with his posts directly relating to having multiple partners with deeper relationships. I am very comfortable with my partner being physical with other people, it doesn't phase me much, but I found myself being really bothered thinking about him having me as a emotional and physical partner along with someone else. Should I be okay with this? Am I being selfish and not open minded? Part of me just wants to keep the deep connection part of our relationship sacred to just us, but is that asking too much and it that not what being open or polyamory really is?

I don't have a ton of experience with polyamory, so any advice is appreciated.