I bought a burger patty that expired in Dec 2013

I bought a burger patty on Sat the 20th of February 2016, i got home cooked it ,made myself two big burgers for lunch.I started eating the burger it was tasting really funny to the extent that i thought it was just a spice or sauce that i used .Half way through the taste was really unbearable and i just thought i should check the expiry date for the patty only to realise it expired 3 years ago..The expiry date on the burger was on the 12th of Dec 2013 and sadly my tummy has really been acting up.I took back the patties they offered me another one i refuse because i really cant trust their stuff anymore and i wanna see a doctor , i honestly think they should cover for that.