Anyone had serotonin syndrome? What causes it? How to prevent it?

This is my third time of going through this horrible syndrome. I have multiple docs and meds and once again one prescribed something (over the counter) that has made me sick for over two weeks. The latest one was a doc suggested I take some cough medicine after I had sent him a message on his portal. He had a list of my meds, but still told me to take this one, MucinexDM, that put me over the top. I am not the doctor or pharmacist. Why can't they get this right? I am upset he did this. I am physically and mentally miserable! Has anyone here got any suggestions in dealing with multiple docs and meds to prevent this?