How's diet? What about your sleep? What about physical activity?
All 3 of these lifestyle factors are the foundation of attention, focus, and concentration.
Stress has an effect as well, if you suffer from chronic stress, meaning your stress levels are elevated the whole day for a long period of time. Like, at least 6 months. If that is the case, you have chronic stress, and it can affect those areas as well.
Not everyone has ADD/ADHD. In fact, together with ASD, it's one of the most overly diagnosed disorder. In some instances because medical professionals don't bother looking at your lifestyle over time before jumping to conclusions; in other instances, because people cheat their symptoms during assessments so they can get legal access to stimulant medication. Both careless behaviours are creating shortages of medication worldwide.
The second behaviour, the faking, is especially prevalent in countries where assessments are just a 1-hour conversation with a psychiatrist that is interested in box-ticking exercise, rather than doing their job. In reality, psychological and psychiatric disorders cannot be diagnosed in good faith like this, hoping the patient and their family are telling the truth. Observation over months and years is necessary. Even asking a parent to fill a form to confirm symptoms and experiences isn't really accurate. In a way, a rushed process is cheating on public health and both public and private funds.