Talk With Your Partner
There may well be an innocent explanation to everything. Maybe he stopped itemizing those bills so you wouldn’t see the twelve-day cruise he bought as a tenth wedding anniversary surprise. Maybe she’s leaving the room because she doesn’t want you to hear her fighting with her sister. There could be something seriously wrong with your relationship, or you could be jumping at shadows.
Regardless of how strong your suspicions are, be sure not to act accusatory. Before you raise the specter of cheating, ask her how she feels about the relationship. Is she getting what she wants out of it? Is he happy with where your relationship is going? The answers to such open ended questions may set your mind at ease or explain your partner’s behavior. If he feels you’ve grown emotionally distant, that might explain why he’s not talking to you about his day anymore. He doesn’t think you’ll care.
If she gives you throw away answers you can follow up with more pointed questions. Explain that you have noticed that he is acting strangely, and you are concerned. A sympathetic ear may be all she needs to open up about how her niece was caught drinking underage or how he’s concerned that one of his friends is in an abusive relationship. Your worries are eased without you ever mentioning the word “cheating.”