I fell behind in my payments.

我付款逾期了。

youdao

I fell behind in my schoolwork.

我落下了不少作业。

youdao

I fell behind, I shall catch up with my classmates.

我落后了，我要赶上我的同学。

youdao

"I fell behind early in the count the first few batters and wasn't locating my fastball well, " Morrow said.

WSJ: Pettitte earns win as Yankees beat Blue Jays 9-4

"I fell behind guys, didn't throw a lot of first-pitch strikes, " Zimmermann said.

WSJ: Werth overanxious as Nationals lose to Mets 2-0