1. He or She use to be someone that was caring, loving and understanding, and suddenly they have become moody suddenly, and eager to start fights? Sometimes, a cheating lover will displace his or her shame, anger, and guilt onto you by starting a fight, which can then be blamed on you. In short, they need a place to throw off their negative feelings. So they can get involve in any activities that will make them fight you.
2. Routine: Is he or she, for instance, coming home from work later than usual on some nights? Sometimes these small changes to a person's routine mean nothing more than life has given them a reason to be unavailable, but they are still something that you want to be aware of, they could be spending time with someone they just met, or having a date with, but do not think too much about it, make sure you ask him about work and what have been going on in his or her place of work.
3. Does he/she allow you to touch, or look through their phone, emails, etc.? If your boyfriend or girlfriend is hiding their phone from you, or deleting all their messages before letting you have it, then there is something they don't want you to see. In most cases they might be scared you will get angry and heart broken.
4. Notice how often they leave the room when they receive calls, especially if he or she was someone that always stay with you when she receives most of her calls. If you ask who called or text ed them, do they always tell you "It's nobody or a friend or family member that often Text them?" These are also important signals, which show that your fiancee, boyfriend, girlfriend, etc. has something to hide.
5. Is your boyfriend or girlfriend is constantly putting someone else down? They may be saying awful things about that person, but pay attention to the fact that they are still talking about them 24/7. They are trying to fool you into believing the person is undesirable, thus throwing the suspicion off them.
6. Do they have other email accounts, or other online accounts? Or begin to, out of nowhere, change their passwords to keep you out of their accounts? Normally, if they didn't give you their password to start with, this is no problem. But if they've suddenly changed it to protect messages they've written, or chats they've had, you should be aware.
7. Has your boyfriend or girlfriend stopped talking to you? Did your significant other always have things to say, and has suddenly become distant? Your relationship may be losing intimacy because your lover has started a new one with someone else.
8. Does he or she become angry when you come over unannounced, or only text you when they are at home, never calling you? These are also signs of a between-the-sheets betrayal. For some reason, they do not want you at their home at certain times, and they do not want to call you while they are at home.
9. Watch for earring on passenger side of the car, or a condom is behind their bed or even in the car, extra time will probably be taken to dispose of those items.
10. Does he smell different when he comes near you? Everyone knows this one is cliche, but it is also true. If he's coming around smelling like a perfume that you don't wear, then he's been too close with someone who wears it or probably hug the person .
11. Have his or her friends begun to act oddly around you? When you casually talk to his friends, do they seem anxious, nervous, or eager to leave? They probably know something you don't know.
12. Notice whether he begins to buy you gifts out of nowhere, or she starts casually mentioning an end to your relationship. Questions such as, "What would you do if we broke up," are key hints. Men and women, both, become guilty. This guilt can easily be forgotten with an action or item for the other person that makes the cheater seem selfless.
13. Catch them in a lie. Casually ask a boyfriend or girlfriend where they were such and such day, and let them answer. Remember their answer, and ask again a few days later. If they are lying constantly, then they will have a hard time keeping up. They may start to get angry with these simple questions, another big hint.
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