I read your question carefully and I understand how distressed you must feel for your doctors not getting at the cause of your issues. Serotonin syndrome is a usually acute condition which requires urgent evaluation and if confirmed usually managed at a hospital setting at least initially. However I believe it is difficult for any doctor in this community to give a responsible answer since serotonin syndrome is related to drug interactions as you say, but you mention neither what drugs you take nor what your symptoms are. Me and my colleagues would be happy to try and help you but please write again by telling us some more about the symptoms, their course in time and the drugs you are taking.