Open Relationship/Compersion. How do you overcome jealousy?

I've been dating my boyfriend for a couple months now. He's been very up-front about his need to be in a relationship where both parties are free to pursue other interests. For him, he's attracted to the mind more than the body, so inherently his FWBs are more than just hookups, they are also people that he cares about. So we are open but we are each other's Primary.

Logically this makes sense to me. I know that I am going to have needs beyond our relationship, and I love the idea of being in a relationship where both parties are mature enough to understand that and allow it to happen.

Yet, I'm really struggling. This is my first time in a relationship like this, and I was not expecting how confusing the emotions would be. I get an anxious pit in my stomach when I think of him with other people that can sometimes bring be to tears. I think a lot of it has to do with it not being purely physical for him, that he cares on some level about the people he's with, too. I guess it makes me feel less special as his Primary?

I spiraled a bit last night and went googling around about open relationships, so I know that jealousy is a thing that everyone deals with. But the concept of Compersion, of getting thrill or ecstasy from seeing your partner being fulfilled by someone else... I am terrified that I will never be able to feel that. I just can't understand it.

If I never experience compersion, what does that mean for this relationship? Am I doomed to feeling this pang of jealousy every time? How do I stop feeling left out or insecure and just be happy for him to be with people he cares about? I really want this to work.