What Causes Bad Odour From The Vagina?

I ve never had an std before & do not know if I have one for sure now. In May this year I was told I had a slight uti after a u.a. was done when I was admitted to the hospital for something else. I had no symptoms like burning when urinating or going more than usual, etc.. I did kinda stink in my vaginal area kinda like b.o., but I thought the smell was bc I had been sweating a lot bc it was hot in my room & I was wearing paper scrubs the hospital put me in after they had me change from my clothes. So the dr prescribed Bactrim for 3 days for the mild uti they said I have. I felt fine & the smell had gone away. After I got home from the hospital I was sexually active with the same guy I was sexually active with prior to my hospital stay. The smell is back. I shower everyday & use Summer s Eve to keep my vagina s pH normal. I did have 2 menstrual cycles in June which is also not normal for me. I douche after each cycle with a vinegar & water douche just to feel clean once my cycle is done. I don t have any burning, fever, chills, itching, discharge or any other symptoms that would concern me. As I ve been reading online apparently not everyone has symptoms if they have symptoms. I don t have health insurance & I don t work so I can t go to the doctor. I do however have a script of Bactrim on hand. Will Bactrim treat & cure me if I do have an std? It seemed to make the odor completely go away before. I have reason to believe my partner has been unfaithful to me. I don t want to be back with him in anyway especially if he s given me a std. I have not been unfaithful & have only been with him so if I do have a std he would definitely be the one that gave it to me.