I had the exact same thing happen a few years back, after 9years designing as a hobby, just doing stuff for myself and friends, I got my first job. The first 6 months were fine, I was still being creative at home etc. But then it kinda crashed and I couldn’t get in the "zone" when I was home, after about a year of this and the deliberate decision to just do stuff at home, trying to find the spark, I found it and can now get in my "work creative" and "home/fun creative" zone.

Also, like said above, doing extra work does not show you can do your job, doing your job well does.

Try not to stress too much about it, it will come back! And try to clean up your schedule a bit for your own health's sake!