Have you been diagnosed with Add by a professional? If no, that's your first step.
If so, maybe you should consider medication. Yes, there are side effects, and you may need to try a few drugs before you find one that works and doesn't cause intolerable side effects. You absolutely want the smallest effective dose--which can vary a lot from person to person.
Find a psychiatrist who deals with ADHD, and take it from there.
Once the meds are working for you, (if they do) then it might be time to consider learning more study/organizational/concentration skills. In a way, the meds can help you learn what focusing is like. Consider an ADHD coach.