I'm tied up at the moment.

我这会儿正忙呢。

I've got so much to do.

我有很多事要做。

I'm so busy, I'd really appreciate any help I could get.

我都忙得四脚朝天了。

I don't even have time to catch my breath.

我连喘口气的工夫都没有。

It's been a long day.

（今天忙了一天。）

I can't leave this job at the moment.

我现在真的抽不开身。