Mrs. H, I fully understand why you are so upset. You have every right to be. This is an issue that your lawyer needs to deal with. When my exH and I separated, I had it put in the legal separation papers that my ex could not have any overnight guests of the opposite sex that he was not married to when he had the kids. Needless-to-say, he didn't have the kids overnight more than once or twice. And, of course, he made sure the same applied to me (which was not an issue).
Is it possible for you to have something like this put in your court documents?