My son is 2 years old and ever since he learned how to sit up he would bang his head of of everything and he doesnt really like to play with others he likes to be by himself
No, he really is too young for ADHD testing. And it is not unusual for a 2 year old to not want to play with others. I am not sure what the head banging would relate to.
Does he talk to you? Make eye contact with you? Snuggle with you?