Pay attention to how he behaves around his phone.
If he acts protective of his phone whenever a text message comes in or a call comes through, it could be an indication that he does not want you to know whom he's talking too. You may see him ignore a lot of messages or calls or take his phone into another room to check on it.
Look at your man's appearance and think about whether it has changed.
If he is putting forth more effort to groom himself, then he could be trying to impress somebody besides you. However, it is important to consider the facts, such as changing his appearance for a new job.
Count the times you have been physically intimate in the past week.
If you're not as intimate and you used to be all the time, then something may be causing your man to pull away. A decreased sex life is not an automatic sign that he is cheating, but it could mean that he is not as emotionally invested in the relationship.
Listen to your man when he talks.
See if he mentions any female names, such as coworkers, new clients or friends. Sometimes men drop the names of their love interests by accident because they enjoy talking about that new person. Pick up on any cues that may lead you to suspect another woman is in the picture.
Notice whether your man is staying late at the office or making excuses for not being somewhere he said he would be.
Suspicious behavior such as this is a red flag that he may be sneaking off someplace else.
Monitor your man's moods.
If he appears more irritable, edgy, grumpy, or apathetic or picks more fights with you than normal, this may be a sign that he is experiencing internal struggles that involve cheating on you or pulling away.
Pick up on his lies.
Pay attention to where he says he goes, whom he goes with and his appointments. If you notice that his stories do not line up, he could be lying to you about where he really is during the day.
Spot important clues.
Look for suspicious receipts, sticky notes with phone numbers, business cards with a woman's name and number written on the back or other clues that seem out of place.
Decide if you believe he still loves you or wants to be in the relationship.
If he stops saying that he loves you, acts uninterested in your life or seems like he is disconnected, it is possible that he is pulling away from you.