What Causes Chills, Extreme Agitation And Restlessness On Taking Psilocybin Mushrooms?

A couple weeks ago I took "magic mushrooms" with a girl I'm dating. I've taken them before, mostly in college, and never had an issue. However, this time there seemed to be some concerning after effects. I had the chills, extreme agitation, anxiety, restlessness, mental confusion, clumsiness, and just an overall lack of self for quite a few days after. I also take Trazedone and some supplements (Fish oil, Magnesium). I stopped taking my Trazedone last Wednesday and things improved dramatically, but I'm still not back to baseline yet. My feeling is that this is possibly Serotonin Syndrome and I should see a doctor to be prescribed Cyproheptadine... what are your thoughts?