Dear Welcome to HM We understnd your concerns I went through your details. I suggest you not to worry much. I sincerely opine that the problem you are facing now is of your own creation. Once you have good concentrtion in a good comedy movie then why no concentration on your text books? That is simply because of your lack interest. Attention span is directly proportional to the task. If the task is interesting, the span also inceases or the reverse happens. One more thing, do not over appreciate your abilities. Such an over appriceation creates high ego and ego defence mechanism activates anxiety which can ruin your future. Forget about your abilities, thoughts, attention span etc. Make your studies interesting with the help of innovative methods. You shall get lot of methods if you search internet for effective learning techniques . If you still need my help, please describe the whole problem in detail and post a direct question to me. I shall definitely help you with psychotherapy techniques to over come obsessive thoughts. Hope this answers your query. Available for further clarifications. Good luck.