I've always been able to handle decent amounts of alcohol. all of a sudden, having just a few drinks makes me throw up all night?

See answer: You probably have gastritis - I would advise you to hold off the alcohol for at least a few weeks and avoid any NSAIDs (i.e., ibuprofen, naproxen, etc). If still having nausea/vomiting, you should see your doctor. Consider taking a 14 day course of prilosec to speed up the healing. In the future, reduce your alcohol consumption so this doesn't happen!