Good luck getting back to work. I personally recognise the "highly productive week" followed by relative unproductive weeks. For me it's a personality thing, and understand when I consider things "done", and what is the "tidy up".

A week of heavy mental activity that completes the design is a lot of fun! Followed by a few weeks of implementation/bug fix/document is not so much fun, and explains my pattern quite well. Trying to find mentally challenging pieces within the slog, and creating challenges for tasks in the slog helps a lot in the quiet weeks.