Food poisoning from expired Juice

On the 11/09 my colleague and i bought Danao fruit juice at Dainfern pick n pay not noticing that it expired 03/09. She had a running tummy and after a while mine also started, when i got home it got worse I even rushed to the hospital where doctor said I had food poisoning I then told him of the juice that I had earlier. I had strong stomach cramps, I was vomitting also had diarrhea. Then went to the store to lay a complain and have my medical bills paid by the store, they told me they would lodge it and give me feedback. Today i get a call saying that my medical report does not confirm food poisoning by law this does not prove the allegations I'm making I need to get test results or proof confirming that I really had food poisoning from their juice. I already incurred medical costs, I have been buying medication since this incident, now i must uae my money again to pay for tests to prove my food poisoning? What proof do they need because it was their neglence that they had expired product on their shelf on promotion even worse that caused me all this, I still have diarrhea even today. I seriously need to take legal action as it shows they not willing to do anything about this.