fall behind with (something)

1. To not be as current with some task as one should or ideally would be. I fell behind with my schoolwork when I had the flu. I've fallen behind with that show—can you tell me what happened in the latest episode? A: "Did the due date get moved up or something?" B: "No, I just fell behind with things when I was out for a week on vacation."

2. To not be up to date on one's current financial obligations. All of those medical bills have caused me to fall behind with the rent. A: "If you'd had more money saved up, you wouldn't have fallen behind with your bills. Just sayin'." B: "Gee, thanks." Because I'm still waiting for three clients to pay me, now I'm falling behind with my own bills.