YOU SAID:

i have to go poopoo in my pants EEEEEEEEEEE

INTO JAPANESE

私は私のズボンEEEEEEEEEEEEEEEEEEEEEEにうんちを行かなければなりません

BACK INTO ENGLISH

I have to go poop to my pantsEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

INTO JAPANESE

私は私のズボンにうんちをしに行かなければなりません。

BACK INTO ENGLISH

I have to go poop on my pants.

INTO JAPANESE

私はズボンの上にうんちをしに行かなければなりません。

BACK INTO ENGLISH

I have to go poop on my pants.