Curious

So, it’s always been a fantasy of mine to have a threesome, however I have only been with one woman (my wife). And I don’t want to ruin our relationship. How can I bring it up with out sounding like I’m not into her anymore? I don’t want to bring in one of our close friends and make things weird between us. So I thought an escort would be alright, so checked some subreddits to get a jest of it; saw some horror stories and decided that’s not a good idea. (If one of those 2 options is better please let me know)