It is not unusua for children to have random thoughts. One has to learn to be more focussed and it does not happen overnight. Neither medication is going to make you more focussed. I suggest that you discuss with your school counsellor and, if necessary, consult a psychologist
who may help you in being more focussed. It is not possible to say that you have ADHD
without having a session or two with you.
I hope I have answered your query to your satisfaction.