why alcohol can make you feel seriously sick when it didn't used to?

[X Ben]

Since 4 years ago (when I was 30) I would drink a fair bit, then wake up early next morning/middle of the night feeling sickeningly nauseously ill for hours - not always throwing up mind you - when this used to never happen a month or two earlier, despite having bigger binge sessions. Had no idea why, one doc tested 'HP' helicobacter pylori (worth getting a test for anyone in a similar position) - negative. Started taking Nexium each day, helped a lot actually - could drink nicely but could still feel really ill. After umpteen web searches, I read about an intestinal bug called Giardia - which you catch in dirty environments but usually goes away after a month, BUT for some people can be chronic and low-level (i.e. you might not know you have it!). Got tested - negative (many false negatives for this bug), so I talked doc into giving me 4 x tinidazole antibiotic tablets regardless, just in case. Take them with food and drink NO alcohol whatsoever 2-3 days prior AND 2-3 days after taking them. What can I say? Now I can drink like I'm 25. Don't take "you're getting old" for a reason - get tested for HP and GIARDIA. And if negative for Giardia - take 4 tinidazole's at once with a big meal and in the middle of a week or 2 with no booze whatsoever (they are otherwise harmless) and you never know. Get 4 x tinidazole from somewhere, anywhere, take AS DIRECTED and see what happens. Good luck.