YOU SAID:

there is a party in my tummy

INTO JAPANESE

私のお腹の中でパーティーがあります

BACK INTO ENGLISH

there's a party in my belly

INTO JAPANESE

私のお腹の中でパーティーが開かれています

BACK INTO ENGLISH

there's a party going on in my belly

INTO JAPANESE

私のお腹の中でパーティーが起こっている

BACK INTO ENGLISH

there's a party going on in my belly