This is Pissing me Off

[Ice]

So for the last couple weeks I've been having trouble consuming alcohol, well hard liquor really. I can manage to have a few beers and feel fine, but whenever I try to drink hard liquor my stomach starts to hurt pretty bad.

It started getting real bad last Friday when I threw up after ONE SHOT of VODKA while I was sober. My friend also got a bottle of Jack Daniels tonight and asked if I wanted to drink. I had all my work done so I said I'll have a few drinks. I started drinking Jack and Coke and after the first couple sips I felt sick as a dog. I literally almost puked.

So my question is what the hell is causing this? I think this may have happened last year, but I'm really not sure. I'm not a chronic drinker either. I usually drink 1 or 2 nights a week and I haven't been drunk for atleast a couple of weeks. All I know is that I'm at one of the biggest party schools in the country and this is REALLY pissing me off. I like being able to drink.

So once again, does anyone have any experience with what I'm explaining?

Edit: Looking at the Drunkards Thread (:D) last time I was drunk was about 3 weeks ago.