newdestiny could be right on about the Zoloft, keep a close eye on it and see if it is indeed effecting to negatively...Can you come off it? Was the horrible anxiety there prior?
If you feel you have low-serotonin, then Anti-Depressants will not simply correct this. They will allow EXISTING serotonin to stay active longer, however it does not build up the raw material for producing serotonin like 5-HTP or Tryptophan does.