How do you know if your friend is being cheated on?
	
	
		So I have a great friend who is practically my brother.  But he is constantly worried about his girlfriend on cheating on him.  They tend to fix things and talk about it but the worry is reoccuring and it is pushing him to the edge.  I worry for him and I want to see if she might leave or cheating on him.  The only thing is this girl used to be a close friend but due to recent events, we are no longer friends, and talking to her isn't a good choice at all... :/  What can I do to help him out?