Stomach Issues

For the past 4-5 months, after I drink a bit of alcohol (2-3 drinks tops, usually beer) my stomach is a mess; it starts rumbling and getting swirly, and pretty soon I have diarrhea for a better part of the next day.  I really don't drink much ever; especially now that my stomach gets so sick after even just a drink now.  (I had one beer last night and my stomach was upset this morning).  My doctor gave me Nexium, saying that the lining was probably sensitive the Nexium would fix it.  No such luck.  I've been tracking it, and it only happens after a drink, no other food or liquids. Any ideas on what's going on with my stomach?