I have a similar condition where the last time I drunk 3 pints of lager I was sick running out of the door I carried on vomiting till 10pm the next night . I thought it was the lager and changed my tipple, I tried bitter , and then Guinness, each time only 3 pints and each time I would vomit my socks up . To accompany this I always get a migraine and I have had enough hangovers to know the difference. Each time I really thought I was going to die, so in reply to your post what ever it is that is causing this problem it is not psychological, when I drank years ago I would go out be sick and then drink more. I know complete pig. But it was voluntary now I'm sick and its involuntary . If I made a guess at a diagnosis it would be allergic either to the alcohol or the chemicals they now put in the beers or have damaged my liver. Either way its a crying shame
In 1999 I had a few drinks after a very stressful three day job interview (it was three days long, so you can imagine how stressful). From around 4pm to midnight I drunk seven or eight lagers before going home and off to bed. Within. A couple of hours I was up and puking my guts out. It was one of those 24hr things of alternating between sips of water and vomiting. I recovered and put the whole thing down to stress, lack of food, too much booze and forgot about it. The following weekend I met up with some friends and poured myself a can of lager before we went off to the pub. After about three sips, I felt a horrible sensation in my stomach, stabbing pain along with the feeling that my guts were being filled with concrete. I stopped drinking. Every time from then on that I attempted even a sip of an alcoholic drink I felt the same pain.
I didn't have alcoholic drink again until 2004, I'd attempted several sips of wine during family meals, Christmas etc. but always the same result. But in 2004, looking into the window of a pub I snapped and decided to buy myself a pint and try to struggle through it to see what happened. The pain wasn't so bad, much to my surprise and I ended up drinking two pints. Afterwards, I felt a strong stabbing pain my stomach and then a feeling off fullness, like concrete in my stomach for a couple of days. A few weeks later I tried again, this time buying a four pack and staying home (in case I needed the toilet, felt sick' etc.) I could drink the beer and did feel some stomach pain and was full and bloat for a couple of days. However, being able to drink again was worth the bloatedness.
Today, 2013, I can drink pretty much what I want and how much I want with some exceptions. Just one glass of red wine will have me puking my guts out within minutes of drinking. Beer doesn't taste the same, I used to drink lager but now all lagers taste metallic and like bile (I have friends who say that what's is just what lager tastes like!) and I prefer strongly flavoured ales. White wine without food, I find impossible to drink without food and not feel sick, with food it is fine although like lager it tastes very metallic to me.
So, I can drink but often I will have waves of nausea that are unlike the sick feeling you get from too much alcohol but more like you ate something dodgy but this passes quite quickly, especially if I eat something.
My conclusion is that my intolerance to alcohol came on, perhaps triggered by stress and then over time diminished to a bearable level so that I can drink - and drink as much as I want to - when I want to. I hope this gives some people hope that they will one day be able to tolerate alcohol again.
Alcohol intolerance is due to the lack of an important enzyme that is responsible for the degradation of the alcohol. Most people improve through time. There is no permanent remedy for the intolerance.
Best thing you can do is to take smaller shots, mix more, or simply switch to beer :P Now days, when I take shots, they are usually half the size of regular. I also notice I have this kind of internal meter. If I space out shots, I take them down no problem. However if I were to do one after another, even within minutes apart, they get exponentially more difficult to down.
Don't fret, you're simply growing up :P