He is suddenly interested in his looks
So he has always been one of those guys who never bothered looking into the mirror more than once, never tucked in his shirt unless he had to, never cared that his socks were smelly, never wore deodorant unless you begged him to, but suddenly there’s a metamorphosis. 
Sudden Over time
He suddenly gets very busy at work and it is not the end of the financial year.
Cold Shoulder
When someone is cheating, it might start feeling like you’re growing apart. He might start communicating less and less with you or become increasingly emotionally detached.
Extreme Niceness
Are they suddenly being overly nice? Allowing you to watch whatever you want on TV, buying you gifts, asking if you would like to go out to your favourite restaurant. For some, having an affair can make them act happier in their life or guilt can make them try to make it up to you subconsciously.
Privacy
Having a sudden need for privacy can be another red flag of a cheating partner. 
Always Online
So you notice a sudden increase in your guy’s online activity. He is suddenly very active on social networking sites and it’s not just old friends he’s catching up with. Check the tag section on instagram (photos of x), his love interest may just be curating their activities. 
Liar Liar
It’s funny when #men think they can lie to you and get away with it that easily. If he has one too many excuses for his actions, confront him. Too many cover ups = trouble.
Dry Spells
 When was the last time you even kissed passionately? Has there been a serious slack in the bedroom department. If you’ve been “dry” for way too long and any effort you make is being met with a negative response, maybe it’s time to bring it up.
Picking Fights
Have you noticed an increase in arguments and fights lately? Does your partner get upset over silly things and storm out of the house or back out of plans? This may give him an out to leave and meet the other woman. If he’s looking for reasons to get mad and leave, be as sweet as pie and block those moves to see how he reacts.
He accuses you of cheating
Another one of the signs of cheating is when he accuses you of cheating. It might seem weird, but many #people do this because of the guilt they feel for cheating. If he has no reason to suspect that you are cheating, there should be no reason for him to accuse you of it.

My advice: Do not make accusations that you can’t back up. But, if you do suspect it, sit him down for a long talk about your concerns. If that nagging feeling doesn’t disappear, you have some choices to make—and perhaps some investigations to start.
Please share with us in the comment section how you caught a cheat.