My fiancé wants to swing and I’m extremely uneasy. At first I trusted him quite a bit. There have been a couple situations I felt betrayed & that he took my trust as naivety. He purposely kept secret the extent of a friendship he knew I would be uncomfortable with. He says that being in an open relationship we’ll have to be completely honest & open with each other. I have always been very open with him, I’m struggling to really believe he will be open with me. Nearly every time we talk about this I panic.

If you panic when you talk about this, try writing it down. You two can have this conversation over text or email - even if you live together, some things are easier to hash out when you have time to think it over and read it over and draft it.

Talk specifically about the situations where you felt betrayed, particularly this issue of him hiding something from you. Point out that if he wants honesty from you, he needs to also be honest with you. If he can’t do that, then this simply cannot work.

It sounds like you are trying to make this work, but he is so unwilling to meet you halfway that he is being dishonest to avoid having to work on meeting your emotional needs. There is a big gray area between “I’m totally okay with this” and “I am absolutely not okay with this,” and he needs to help you navigate that space. If he’s insisting that you do 100% of the emotional work while he experiences zero consequences in your relationship for his choices, well, that’s a problem and he is not a healthy person to be in this relationship with.