I can imagine the difficulty that you're facing. You are feeling anxious, overthinking and not able to concentrate and it is affecting your personal and professional life. Most of the symptoms that you described indicated an Anxiety Disorder with maybe Depressive symptoms. Anxiety and Depression even in its most severe form are treatable. You will need to consult a Clinical Psychologist for a detailed evaluation and he/she will help you with a treatment plan. If it is severe you will have to take a combined approach, consult both a Clinical Psychologist for therapy and a Psychiatrist for medicine, if need be.