From my experiences, you might wanna look back and seen if you've done anything wrong, even small things, small, but important things get to guys sometimes. But a lot of guys will start to ignore you if their feelings have changed, either for better or for worse, or if something is going on at home. Think about anything you might've done and say something about it, but if that doesn't work then ask him what's wrong or if his feelings have changed at all.