Both my husband and i got tested for std and it came back negative, but every time i have unprotected sex with him few days after i get a smelly disch?

See answer: Bacterial vaginosis (BV) is the most likely cause of your symptoms and is the most common vaginitis in women of childbearing age. BV is not a STD but reflects an imbalance in the vaginal ecosystem occurring when abnormal bacteria outnumber the normal ones. The primary symptom of BV is an abnormal, fish-like odorous vaginal discharge which noticeable especially after intercourse. Rx: metronidazole

It could be as : simple as a fungal infection. (which is not an STD). See gynecologist for examination and prescription