How to get my 5 year old to be a happy kid?

I ahve a five year old sone, he is always very serious and ill. I try to play with him but he gets mad at me if I sing or dance or do anything like that...he acts like its emabrring. He gets mad if i praise him too much...like the other day he was trying to put his own seat belt on...I said " good job, I didn't know you could do That" He just got mad and let go of the seat belt and said " i can't". he gets mad over every thing. Whn we go to grandparents house and they are excited to see him he will stomp off and go sit on the couch pouting even though he has cried to go see them. when i try to talk to him he seems upset by how he acts. he hates to hug people and forget kissing. I am lucky to ge a goodnight kiss......He has his time when he is very fun loving and happy but anytime he is out of elemnet a little he gets ill....I try to do things with him but he either doesn't want it or he gets mad half way through...we tried to get him to play baseball... b/c he is really good at it...but when we got out there he wouldn't play in front of people. WE even isted to help him be comfortable but he still wouldn't play. I wanted him to do karate..but he is scared of people looking at him. I don't want him to care about what others think...I want him to enjoy being a kid......I have tried everything...he has seen phycologist....they said he had ADHD...but treatments don't fix this...I ahve an 18month old daughter who is nothing like this she is the happiest kid in the world....just laughing and playing and never meets a stranger...When we take my son places he gets mad when people say " hey Buddy how are you" he will not speak to them. I try to get him to help me cook and he will get half way through and get mad about something or get mad when i say " thats a great job these are gonna be great" He is extremly intelligent...he has been evaluated as being a gifted child with an incredible amount of intelligents.........He is ok when he brings his report cards home ( which has never been less than a 100 on anything) But all we can say is " thats great we are very proud" if we go over board to praise him he gets mad! What do i do?