get behind in (something)

1. To not be as current with some task as one should or ideally would be. I got behind in my schoolwork when I had the flu. I'm sorry everything is such a mess, I've gotten behind in my filing. I don't think I did well on that pop quiz because I'd gotten behind in the reading.

2. To move or act more slowly than someone else. I got behind her early in the race and could just never catch up. Come on, you stragglers! Please don't get behind in our walk to the park! A: "I didn't expect you to get behind in the race right from the start." B: "Yeah, well, that's what happens when your car stalls at the starting line."

3. To not be able to satisfy one's current financial obligations. All of those medical bills have caused me to get behind in the rent. A: "If you'd had more money saved up, you wouldn't have gotten behind in your bills. Just sayin'." B: "Gee, thanks." Because I'm still waiting for three clients to pay me, now I've gotten behind in my own bills.