What have you been doing seems like a question you would ask someone if you have not seen them for some time. If that is the case, I would say '你最近都在做什么?', something like 'what have you been doing lately?' However, your translation is correct as well, 你一直都在做什么. It depends very much on the context.

what have you been doing ? -你在做什么？

Haha. Thanks a lot.

Perfect! I don't think your translation needs any correction.