Amitriptyline has nothing to cause internal thoughts, though it might help in getting relief from irrelevant and excessive internal thoughts. It's common side effects are dry mouth, constipation, blurred vision, sedation which happens in ~10-15% of people taking the pill. I advise you to continue taking it if your psychiatrist has prescribed same.
Regards.
Next Steps
Nothing
Health Tips
Daily exercise (any) for 30-45 mins.