Is my body rejecting alcohol?

I'm not a heavy drinker, I never got even close to being drunk. But whenever I drink alcohol my body seems to reject it. Sometimes after a glass, or sometimes even just after a few sips of beer, my stomach gets sick and upset and I feel like throwing up (which I manage to avoid). I'm not trying to drink to get drunk or anything, but it does cheer up a bit and I think that's nice. But most times I can only drink so little until I get sick. Why does this happen?

First of all, are you trying to drink on a empty stomach, if its a possibility try eating a meal an hour or two before drinking
Apparently milk is good for lining your stomach and its good to drink milk some time before drinking alcohol.
Once i drank a whole bottle of cider and felt nothing, the next morning i spent an hour in the bathroom puking, i hadnt eaten for most of the day before drinking...