Serotonin Syndrome or Virus?

i had these weird symptoms a couple days ago...first couple days my legs ached, then it moved to my body, then at night all the sudden my whole spine felt stiff and i had tremors,felt like i was going to black out, got really sweaty, had a small fever 99 and i felt very irritable. i cant tell if i have a virus or if it is serotonin syndrome?  it seems like i get this uncomfortable nervous system sensation about once every two weeks, but usually just mild but i feel very irritable.  i am taking lexapro and a take this herb called kratom for anxiety.   I read about kratom and it said there has not been any discovered anti-depressent properties.

[Roger Gould, M.D.]

The problem with taking herbs is you never have any real information about how much of the active ingredient is any batch so you may be having an effect from kratom,and you may want to discontinue it to see what happens to your symptoms.