Thank you for asking. I can understand your concern. Overthinking can be a symptom of anxiety. For diagnosis of a Disorder, one should also have symptoms of sleep problem, negative mood, bodyache for sufficiently long duration and should interfere with individual's ability to function. Poor concentration, depressed mood also suggests a possibility of anxiety disorder. Probably a Generalized Anxiety Disorder. Importantly, it can be managed and treated. Before we plan a suitable treatment plan, the complaints must be enquired in detailed and a thorough evaluation of its severity is needed. With therapy and relaxation techniques one can learn to relax ownself and control anxiety.