I’ll never understand why some polyam people feel the need to move at the same speed as their partner. It’s not a contest. If a partner tells you they are uncomfortable with you moving at the speed you’re moving with someone new, then they certainly have a right to feel how they feel, but they don’t have a right to expect you to modify how you relate with another person in order to appease their discomfort.

You chose to do so with Cheddar, which was your own decision to make. That being said, if I were Swiss and found out that you were the sort of person who would allow your nesting partner’s emotions to hold weight in the relationship you share with me, then I don’t know that I’d be comfortable being partners with you. No one who isn’t part of my relationship will ever have the right to make decisions regarding that relationship, and I won’t ever be partnered with anyone who will make decisions about my relationship with them based on their other partner’s jealousy. That is a very firm boundary of mine.

It is okay to acknowledge a partner’s feelings and work with them to help them feel better while still holding to your boundaries. If you had done that, then you wouldn’t have felt the need to retaliate the way you did due to your own jealousy once the tables were turned.

Both of you would do well with a more secure attachment style. Go read Polysecure by Jessica Fern together.