YOU SAID:

my cat is sitting in my lap but i have to pee

INTO JAPANESE

私の猫は私の膝の上に座っているが、私はおしっこをする必要があります

BACK INTO ENGLISH

My cat is sitting on my lap, but I must pee

INTO JAPANESE

私の猫は私の膝の上に座っていますが、私はおしっこをしなければなりません

BACK INTO ENGLISH

My cat is sitting on my lap, but I have to pee

INTO JAPANESE

私の猫は私の膝の上に座っていますが、私はおしっこをしなければなりません

BACK INTO ENGLISH

My cat is sitting on my lap, but I have to pee