Well, you certainly have some tough soul-searching to do on the road ahead. It says a lot for you that you're not trying to change (or dictate) JC, you're just trying to figure out what you should do about the situation for you.
Whatever you decide, take your time about deciding it. Sometimes we experience something that at first seems impossible, like we just can't do it ... but then later on, we find that it unexpectedly becomes more manageable for us. You may find that you have more strength for this situation than you thought you had.
"At this point I don't know why I accepted the idea of polyamory. Why I let JC have a relationship with Bee. Was it because I am poly or was it because that is what JC wants?"
Well that's certainly something to think about, and interesting questions. Just remember that however you got here, you now know that it is something JC wants. You have to figure out whether you can live with that part of his nature. If you can't, then it will come down to, either he'd have to change (and break up with Bee), or you'd have to break up with him. None of the paths you can go on are easy paths. So as I said, don't be in a rush to decide anything. Give yourself some time to maybe acclimatize to this new kind of situation.
Think about what you will need to get you through this impending trip that JC is going on. Will you need him to contact you very often? Are there things you can do (friends to see, hobbies to work on, etc.) that would help take your mind off of some of the fears and loneliness? What else could be done that would make this a little easier?
I hope things work out okay.