threesome with husband?

So my husband has mentioned a threesome in the past and lately I've been curious about the idea. I'm very curious about being with a woman but I don't want to cheat on my husband so I haven't l. I'm considering having a threesome, but I don't want to regret it. I'd be devastated if my husband cheated, but if we both had this one night and that's it, I think I'd be okay. Anyone do this and regret it? How did it affect your marriage?