For those who have been cheated on...

I am curious as to what subtle signs were you getting that your SO was possibly cheating?  
Now I am not talking about the obvious "I caught him in bed" or "I saw the text and pics on his phone"... I wanna know about the little things. 
Was he distant? Or overly loving? Did he have a bad temper randomly? Was he texting more? Going out with his buddies more? Was he working out more? Etc.