1. Changes in normal routine: work, home, sex, schedule. 2. Eager to start fights. 3. Loose interest sexually or make excuses to not have sex. 4. Steps out to check calls. 5. His friends may act weird around you. 6. Change in interests such as taste in clothes, music, etc. 7. He may talk about a girl he likes in a harsh way to fool you into believing he despises her. 8. He smells weird when coming from work/ heads straight for the shower after work, unless he works in a place where he needs to wash off dirt or chemicals. 9. Won't want to check his phone or mail when your around. 10. Probably the most important thing u should do is check his phone bill.
My mom just had a feeling. Strange phone calls/hang ups. Checking his cell phone like way too often. Looking at expensive gifts he never gave her. Having to leave at a weird time to go somewhere. Lost weight-changed clothing style-used words we never heard before. She just asked him and he denied it but it breaks our hearts to see him drift when she tries so hard :(