Milk is making me feel sick and have a really bad stomach ache.. and some food that i eat aswell what could be the cause?

Food Intolerances ..: can be very common and appear in some people over time. Gluten in wheat is the most common offender and dairy is next. Some people are intolerant to lactose (milk sugar) and/or casein, the milk protein. If not sure, eliminate all milk and things made from milk for a few weeks and see how you feel. Eat a balanced diet of natural foods otherwise. Later try milk once and see if u get sick.