Recurring Yellow Vaginal Discharge, Negative STI Test, Sexually Inactive Since Years, History Of Chlamydia Treatment. Misdiagnosis Chances?

I did a pap smear when i noticed i had a yellow ( no itch, no odor) vaginal discharge . When I saw my General Practitioner for my vaginal discharge she prescribed metronidazole tablets for me. It didn t help. I saw her the following day and she did a vaginal exam and prescribed Canesten (tablets) ( clotrimazole ) and doxycycline and suggested that it was chlamydia . I really saw a great improvement while using these medication. Now that it s done my vaginal discharge has reappeared. I did an STI test containing ( T.Pallidum IgG/IgM, HIV,Hep BsAg, HTLV 1&2) which all came back negative way before this vaginal discharge became present, I have been sexually inactive for 1 year 9 months now. I m more concerned and now starting to worry why the discharge has reappeared, why am I going through this even if I ve been sexually inactive for almost 2 years now? Is there any suggestion as to what I m experiencing.. or why this has reappeared? Have i been misdiagnosed?? Also I am on Depo Provera could this be causing that? NB: The pap smear results have not been returned ( still under review).