Why does my stomach hurt so bad?

There are so many: reasons, including stomach ulcer, but i would never guess. I would make appointment to see your primary care doctor who might suggest you start Zantac, (ranitidine) but make appointment

Stomach pain: Hi, too many reasons, including inflammation of your inner layer of stomach called gastritis due to alcohol, some medications, infection, ulcer, food poisoning and etc, you need to see a doctor for full history and examination, best of luck.

General check up: I will recommend a general check up with your PCP, he/she will conduct preliminary evaluation and refer you to a specialist if need be. Your symptom is non-specific and may or may not be serious. It's very difficult to explain why your stomach is hurting without proper history and examination.