Should I get my son re-evaluated?

My son was diagnosed with ASD last year at 4.5 years old. I have always questioned his diagnosis because I never suspected he ever had an issue until his preschool teacher showed some concern over his social skills. He was a happy, engaging, loving baby, always wanting cuddles and to be held, babbling, chatting, always very curious and wanting to learn, learn, learn. He never played with toys in an odd way, never had sleep issues, made good eye contact. He used to move his hands when in the car or pram, that was all.

I did all of the therapies with him last year just to cover "all the bases" because I just didn't know what he needed, yet we were given all of this funding, but after 6 months, all therapists let him go. He is in kindergarten now in a mainstream class with no teacher's aide. He has some lovely friends that he plays lots of fun and interactive games with, plays lots of imaginative games with his sister, his handwriting is beautiful and very neat, he's an avid reader, and he is very, very bright (his teacher gives him separate homework to challenge him).

He is not fussy with foods, is an excellent sleeper, does not follow any strict routines or rituals, and never has meltdowns, ever. He is loving, kind, affectionate and self-sacrificing. The only thing he does that represents an autistic trait is he shakes his hands when excited or nervous