He will start to show interesting another girl.
He won't get back to you as often in text
He will ask you about your friends/friends
He won't want to hang out with you as much
His schedule will get even more busy
Things will get between you without him caring
He'll be more distant
If all of these things happen, bring it up to the guy and if he pushes it away, the relationship is ready to end and you have every right to end it. Good Luck!!!!