Why has my daschund being ugly lately?

He just turn 2 years old 2 days ago. After that he's been mean to everyone. Before when I sleep and someone comes by me he gets all protective and we thought it was cute. But now when my mom was joking with him. He growl at her and came to me all scared. Then today there was a dog outside and he was friendly. Well I checked the dogs collar and went to pick it up to bring it home and my dog chewed its tail.. poor dog ran home scared :(.. Is this normal for him to act like this?