Translation:I am working right now.
Isn't "I'm working" acceptable since it emphasizes continuing action?
With 正 an equal emphasis is put on the point of time. Thus Duo's translation is good. But your answer should also be accepted.
正 means "right at this/that point" and is an emphasis of the timing of the continuous action. 现在 means now, but although it has the 在 character in it it does not eliminate the use of a 在 again to indicate continuous action. That said, usually when we say 我在工作, it is pretty rare that we would add 现在 as it is well understood when used verbally. As to 我现在工作, it would be used when we tell people we are about to start working (but haven't started yet).