How do you say "my stomach hurts" in Japanese?

Question

Answer

If you mean the part of the body containing the stomach; belly or abdomen.
You can say おなかがいたい．おなかが痛い．

If you mean particularly organ, stomach.
You can say いがいたい．胃が痛い．

Answer

わたし　の　おなか　が　いたい。watashi no onaka ga itai.
You can skip the "watashi no" and just say "Onaka ga itai"

Onaka(お腹) means stomach, or abdomen. And itai(痛い) means hurts. :)