Well, we are never entirely free are we
I try and think of it as that I am committed to certain things, people, places, whatever and not see it as lack of freedom... but that is another story. Still, it has helped me with my jealousy. My investments are huge when it comes to people, I have expectations of them and myself and assume much... its only human after all. I need them. Bottom line. I spent years denying that and just as many trying not to but truth is that when other people come into their lives that they obviously love as much or more than me that is very threatening to my inner self. Sure, I can rationalize it to death in terms of theory, but the fact is, its a human thing to feel threatened in this way.
If I were in this situation I would be getting to know my new metamour, deciding if they are someone I can find a way to bond with and if not accepting that I might not and finding peace with that. Knowing my metamours has helped me walk through the jealous/envy feeling the most.
I also do my best to entertain myself and do all the things I don't get to do because my time is taken up by my partner. I do a LOT of self care, self reflection and work on self love. Sometimes that means going to visit old friends or spending time with friends that love and cherish me the most.
The other thing I do is make sure I am on top of communicating every little thing that comes into my head. Even if its to say, "yup, still in this feeling" to my partner. I make sure they know every little thing that could help me feel reassured, right down to the words I need to here. I don't leave them assuming or expecting anything and don't assume and expect anything in return. EVERYTHING must be out in the open in order to have conversations about how to move forwards.
Then its about waiting.... sometimes for a long time. This feeling you have will dissipate and it will get easier. It will likely happen faster if you put all the hard work into it you can. Things will come up that you hadn't expected, deal with it, get through it, don't leave any stone unturned, because in my experience, those stones can be thrown in moments where there is the realization that hiding from such things is just not going to work. Even the smallest thoughts come back to haunt.
You might want to write in the meetings and events section about finding community in your area. Maybe you should start a group that meets to talk about poly and relationship dynamics. That is how I found my closest friends and found a huge support network. So worth the effort!