How can u tell if the problem is ADHD?

It might help to ask yourself some questions about your child's behaviour. In fact, if you've talked with your doctor about your child's behaviour, your doctor may have already asked you some of these questions.  

How long has my child been too active? Hyperactive children with ADHD have had problems with hyperactive, impulsive behavior since before age six.  Also, children with ADHD are often described by their parents as being fussy and difficult to quiet in infancy. Sustained restlessness, even when eating or at bedtime, is characteristic of children with ADHD.
Is my child's restlessness and impulsivity a problem in several different settings? ADHD is less likely to be present if your child only shows behavioural problems at home, but not in other places, such as at school or at the grocery store. 
When my child is misbehaving, is he off in a world of his own or is he looking over his shoulder to see if I'm watching him? Children with ADHD cannot control at least some of their hyperactive, impulsive behaviour. Suspect ADHD if your child appears "off in a world of his own" and does not respond to you when, for example, he is climbing on a table, jumping on the sofa or misbehaving in some other way. 
Am I primarily angry with my child or am I primarily frustrated? The hyperactivity of children with ADHD is irritating, but parents can sense that their child simply can't--as opposed to won't--sit still or quiet down. This is frustrating.
Can my child stick to activities, or is the house littered with a trail of unfinished games and projects? Children with ADHD often lose interest in an activity in five minutes--or even less. They go from one activity to another, and another and another. You may ask your child many times to clean up, but he or she will not even be able to focus long enough to do that!
My child can watch cartoons on television for a long time. Does this rule out ADHD? Children with ADHD are often able to keep their attention on the fast-paced world of cartoons and video games. If your child's attention stays glued to the screen for programs such as cartoons, suspect ADHD. Often, such children will keep their eyes on the screen, but will be constantly fidgeting their legs and arms.