I need to go number one really badly.
I urgently/ badly/ desperately need to pee.
I am bursting for a pee.
I need to go number two really badly.
I need to take a dump / crap desperately. / badly.
3. 我好急. (不想提及大便定小便, 對不熟的人的說法)
I need to answer a calling from nature.
Excuse me! I have got a call of nature!
I am caught short!
I have to empty my bowel. 大便/ empty my bladder 小便
Do you need to go potty? 去洗手間
She has to take a wiz. 小朋友要去小便 (較文雅的說法)