I was on doxycycline for three months for chronic prostatitis. I had similar bad side effects start last week, nausia, pain in the stomach, weakness in the legs, exhaustion, dizziness, etc... But no depression "yet". I have been off the doxycycline for four days and still having bad symptoms. I read your posts --- Thank you! I have read that doxycyline depletes the body of B vitamins. Many of the symptoms described by many of the posts are similar to depletion of B vitamins. Have any of you been tested for B vitamin depletion?