Well, since you mentioned he does have some sensitivity (although most little kids do), you might want to check out this video on sensitivity
https://www.understood.org/en/learning-attention-issues/personal-stories/stories-by-kids/video-a-childs-view-of-sensory-processing-issues
Thanks so much for the reply!, I've only just logged on to read.. He has a bit of sensitivity towards lights and loud sounds! He has done from he was a baby and he hates anything inflated .. He has no trouble falling asleep at night though he hasn't napped during the day since he was 13 months old.. The whole thing never even crossed my mind I also noticed certain we things but think it's all fairly normal only some family members and friends started waving the word ADHD around at me all the time so I figured I'd look into it! .. He is very fidgety even when he's standing he shakes like hes holding in a pee or something but he isn't he just can't sit at peace lol x
Really at this point in time its hard to tell. A lot of his behaviors are typical 3 year old stuff. They really are like a new little puppy.
The only two things that might point out to something like ADHD are the constant running around and the short attention span.
I guess my first question would be - does he have trouble falling asleep at night? That might be a stronger indicator if he cannot wind down at night.
Also, does he have any unusual sensitivities to food, textures, light, or sound, as this would be an indication of something like sensory processing disorder. Which would be a good thing as it is easier to deal with.
Overall, I think it is too early to tell what is going on. And I tend to doubt that a pediatrician could really help much at this age.
Probably, one of the best ways to tell if this is unusual is to get him into an experienced day care situation for a small period of time each week. Make sure it is not one that requires naps! (and you certainly don't have to do this now - but perhaps at 4 years old). Seeing how he reacts to a slightly structured environment and how he then compares to other kids his age is very informative. And if the day care provider has been in the business for years, their input will be very helpful.
Now, just for the heck of it, lets assume he does have ADHD (since you posted on this forum its gotta be in the back of your mind -oh, anybody in the immediate family with ADHD?). Lots of kids have ADHD. There is a ton of information on how to deal with it - I literally have hundreds of helpful links to almost any question. You really can't do, and probably shouldn't do anything now. However, if he does have ADHD, what you can do is to learn all that you can about it, so that you are not punishing him for things that he cannot control. And as you will find out, there are a lot of things (besides meds) that you can do for him to help him.
I don't think that the mimicking and copying are ADHD related. Kind of think that it is a way of getting attention. And certainly a way of learning language skills, but really don't know much about it - except never have seen that come up related to ADHD.
Ok, to sum up - I really hope I haven't freaked you out. He may or may not have something like ADHD. I have this post on my "watch" list. At any time, you get more info or have any questions - if you post to your original question. I will see it. I have been the CL here for lots of years and don't intend to stop any time soon. So even 3 years from now - you post, you will get a response from me.
So, enjoy the heck out of him. This really is a precious age. He is perfectly ok now - might need some tweaking later on or not. Keep me informed and certainly ask any questions you might still have. Best wishes.