Be direct and ask him if he's cheating on you. He may lie or he may tell you the truth. But either way, he will know that his relationship with you is in trouble. Don't let him off the hook. It's time to talk about boundaries and trust issues.
Read How to Detect Lies. This article will help give you the skills to determine if your boyfriend is lying. Most people are bad liars. All you have to do is turn up the heat and watch what happens.
Note: once he knows you're suspicious of his behavior, he might work overtime to cover his tracks. If so, you'll need to be more vigilant.
Check his mobile phone for phone calls or text messages from other girls. If you can get your hands on his mobile phone bill (on paper or online), you might be able to see who he's been talking to and texting with. Long conversations and lots of texting to one particular number are red flags.
If your boyfriend tends to misplace his phone, another thing you can do is simply take it and let him assume he lost it. Don't answer it or anything; simply see who calls or messages him.
Check his email, Myspace, Facebook, and instant messaging accounts. Many times, cheaters use the Internet to carry on their sneaky business. Check his computer often to see if he forgot to log out. Don't respond to messages as him, however - that's an easy way to get caught spying before you catch him cheating!
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