What to do if i do not know how to stay concentrated for very long and my attention span is too short?

See doctor: It is best to see a doctor for a full evaluation. Then if you have a diagnosis the correct treatment can be chosen to help you

Mindfulness: There has been some good evidence that mindfulness training and meditation can help with concentration. Look for a place near your home that can teach you these practices.

Agree: This is unusual to emerge at your age. If no physiological findings perhaps psychological testing.