If you think that your spouse is cheating on you, it can be an upsetting time for you. Perhaps the biggest sign of a cheating spouse is their need to keep everything private from you. This is especially true if they hide their cell phones, bills and if they have one, their computer. This can also make it difficult for you to find out what they're doing. In regards to the computer, which they may also be using to contact their lover, can also be a strong tool to find out the truth.