Sorry to hear that it didn't work out.
From my perspective, it is hard to adjust. T has always been involved with others while we have been together. Time and trust are has what allowed me to deal with her time with other men.
It does get easier, especially if you want it to happen, and she's willing to talk. I suspect you'll be much more relaxed next time the opportunity occurs.
Me: 41 straight male in a V with
Wife: Kay - mono female - married 19 years
LDR girlfriend: Susan - poly female - 4 year relationship
Stakes - very intimate friend
Ironically named Farmgirl - local interest