I get sick from a lot of foods and drinks that i consume, but mainly milk based products. what's the reason for this?

Lactose Intolerance: You most likely have the common problem that a lot of adults get which is a lactose intolerance or lactose allergy. This is easily treated by avoiding dairy products and/or taking lactaid.

It is possible: That you have lactose intolerance. See if the same happens when you consume lactose free dairy products. U find them on every supermarket.