Welcome to the site! There is a ton of great info and a lot of great people always willing to give advice, so ask away with all of your questions
Lionheart's post is right on the money and touches on things that are absolutely true. Some (most) people just aren't cut out for swinging, and absolutely nothing wrong with that. I too am a big believer in people need to do what's right for them. I think the cause for a lot of bad or failed relationships is when external influences (work, toxic friends and family, societal pressure, etc.) and/or selfishness within the relationship (cheating, dishonesty, etc.) are allowed to override that innate feeling that a couple develops of what's right for the relationship. There are those that shouldn't swing but do, those that should swing but don't, those should swing and do, and those those shouldn't swing and don't. Odds are people in those last two are having the best overall relationships since they are going with what they know is right for them.
Another important thing is a word you don't see very often. "Compersion", which means taking happiness in someone else's happiness. So if you see your partner happy from enjoying a great sexual experience, no matter who it's with, that makes you happy. For most people, the negatives of even thinking about or especially seeing your partner with someone else block any compersion. They likely share their partner's happiness at other things, career achievements or whatever, but it doesn't extend to the sexual realm. With swingers, that line isn't there.