Brother issues

I know that I am not a parent however I assumed that this forum would be the most appropriate for my question.  My 17 year old brother has always been odd but recently things have gotten worse. My brother will come up and hug you for no reason even when you would prefer to be left alone, he always wants high fives, and can get very frustrated if you ask him a question or to do things. This behavior is even stranger with the fact that he is a brilliant know-it-all. he has always had a very creative imagination. He rarely ever goes out of the house anymore only to go to dungeons and dragons meetings with his friends. He has also gotten more irritable and almost anything can bug him. He seems to always switch from acting goofy trying to purposely annoy me to no end. That or he gets into another mood where he gets really frustrated, and frantic. The  he'll ask if we love him, or if he is ugly, he says These things quite often.  Please any insight into this situation would be much appreciated.

[Shadowfluffy6]

it sounds like my dad and a teacher at my school.