only low platelet count
does not signify leukemia. your complete blood count
to be mentioned . if indicated bone marrow biopsy also to be done . low back pain
may be due to connective tissue
disorder. may be due to other diseases. X-ray of L-S spine report to be mentioned. anyway venlafaxine is a antidepressant category drug may be used for multiple indications, not seems to be related with your present symptoms. consult your physician.