Effexor + St. John's Wort = Serotonin Syndrome?

I know they say that you are not supposed to take St. John's Wort if you are taking an antidepressant, because it can increase the risk of Serotonin Syndrome. But here's the thing. I only take 75mg of Effexor a day. At different points I have been prescribed twice my current dose of Effexor, Paxil along with the Effexor, and Prozac along with the Effexor. The increased dose and the SSRIs all caused unacceptable side effects, but not Serotonin Syndrome. So, I'm thinking....since I take a pretty small dose of Effexor, and since my Dr. saw no problem with prescribing more antidepressants, adding St. John's Wort should be safe, at least WRT Serotonin Syndrome. My doc is pro-prescription-drugs and therefore won't give me an opinion.