I have slight yellow discharge sour smell. i went and check it is not sti but i only have normal white discharge 1 week after period the rest is yellow?

There are many causes of vaginal discharge other than common STDs. You also need a PCR test for trichomonas (a common STD, but often not included among routine STD tests) and can cause strong odro. Bacterial vaginosis is another possibility. You need a careful pelvic exam, and maybe retesting for gonorrhea and chlamydia too. No sex until this is sorted out. Good luck.