Shoprite selling expired goods

I bought cookies on the 20/04/2018 at Shoprite Carletonville. I indulged that night. The following morning i had a running tummy. I checked the expiry date only to find out that they expired on the 26/03/2018. my running tummy went on for three days. i went back to the store and lodged a complaint. i asked if they would pay a doctor so i can go for consultation but they told me i must come with proof that indeed it was the cookies that made me sick. I tried explaining that I am a student and cannot afford a doctor ... the lady explicitly told me that she cant help me as i have no proof. what makes me angry is that this is not the first time, the one time i bought yogurt only to find out it expired three days back.