Feeling very sick and ill today

Wish I knew what was wrong with my stomach. Been feeling sick since Sunday, and it seems to get worse after I eat anything. On Sunday I was ill as a result of drinking too much on Saturday night, but I can't still be suffering from the effects of a hangover, surely? ... And besides, I've had this kind of stomach pain before when no alcohol was involved.

I've been to doctors about it before but they just say "it's a stomach bug, now sod off" or words to that effect.

Just sick and tired of feeling ill all the time. :-( And not looking forward to trying to do an interview in two hours' time, since I have a choice between being so hungry that my stomach's rumbling audibly, or risking being doubled up in pain, neither of which looks good to prospective employers.