The feeling that somebody is in your house may annoy you sometimes. But firstly you need to check whether this is only your suspicion or a realistic feeling. In this situation you should stay calm. If you are sure that someone is in your house you should immediately call 911 and tell them your situation. Sometimes the feeling that someone is in your house may be caused by a kind of social paranoia where one thinks as somebody is trying to harm him. In this case you should attend some counseling sessions. But if you think that someone is there for sure, you may dial to a nearby police station or to any of your friend.