YOU SAID:

I peed myself I had to pee so bad

INTO JAPANESE

私はおしっこをしたのでおしっこをしなければならなかった

BACK INTO ENGLISH

I had to pee because I was peeing.

INTO JAPANESE

私はおしっこをしていたのでおしっこをしなければならなかった。

BACK INTO ENGLISH

I had to pee because I was peeing.