vaginal odor

Im 4o yrs old and for the past 7yrs i've had a foul smelling clear discharge and it gets worse right b4 my menstrual. I had the depo-privera birth control shot and went without a menstrual for like a year about 7yrs ago. Do you think that since a woman's menstrual is a form of waste leaving the body and since I had no period for a year, that this may be built up waste? Went to the doctor and took test, I have no diseases or infections. Can someone please tell me what I could to get rid of it, because it has to be something internally. Please Help