Here's the answer:
“我憋不住了”
(wǒ biē-bú-zhù le)
Watch a real native speaker say it:
Here's how it sounds in a textbook:
Fun fact: the hundreds of thousands of people learning Chinese with Memrise get this phrase correct 86.47% of the time!
(wǒ biē-bú-zhù le)
Fun fact: the hundreds of thousands of people learning Chinese with Memrise get this phrase correct 86.47% of the time!