Many people misunderstand that ADHD refers to children who are restless. Restlessness is only a symptom of ADHD and other conditions can also result in restlessness. It is important to do a through workup before labelling a child as ADHD. Since there were difficulties in birth it absolutely essential to do a through examination. This includes assessing when developmental milestones were reached, if there are any stereotype behaviour and intellectual ability. Only the should a diagnosis of ADHD be made.
You have not mentioned if any medicines were prescribed. There are many very effective medicines for ADHD. Please consult for a proper diagnosis
Next Steps
I would suggest you consult with all medical records, treatment history and get a through evaluation done.