4. Defensive about their phone
A healthy relationship is built on trust. If you are not cheating then there is nothing to hide and your partner’s phone and email accounts would be open for you to see. However, if you see your partner guarding his or her phone a bit too much then you should know something is wrong. In fact, every time you hold their phone, you will notice them get a bit anxious and will try to hurry you to giving them the phone back. This is a clear sign that your partner is cheating on you.