I have to pee like a monster
You're so desperate to pee that you're ready to fight anyone who stands between you and the nearest bathroom.
At the mall, I had to pee like a monster. I pushed through a group of kids just to get to the bathroom.
During a class presentation, I had to pee like a monster. I said, 'I need to go now,' and left mid-sentence.
During a video game tournament, I had to pee like a monster. I took a break and came back to win.