Just echoing Brandon, do NOT tell ANYONE that you are going to contact the OBS! Even your WW! This is how it will go if you do.... WW will tell OM that you are going to tell his wife, he will then tell his wife that a "friend" of his has this crazy jealous husband who is controlling, possibly abusive, and he's always accusing her of cheating on him if she so much as looks in another man's direction and now, this crazy man is accusing her of cheating with me. The OBS will say "oh my gosh, that's so terrible, that poor poor woman. I will not believe a word he says if he calls me because I love you and trust you, you didn't have to tell me this of course so it must be true". You will then call the OBS and she will either listen and not care, or she'll call you a liar and inform you that you are the devil on earth for making up such malarcky.
Whatever you do, WHATEVER you do, do NOT tell anyone you are going to tell the OBS until you actually have done it. You WILL regret it.