Have you had a lot of weather fluctuations up your way? Not always, but often, I find my self in a bit more pain when the barometric pressure drops and the cold, wet/snowy weather come in. Not just in my other arthritic joints (back, etc.) but in the tissue around my new implant.
A close friend who had a replacement at age 16 and 5 revisions since then said it still happens to her sometimes as well---almost as though if she'd had a busy week and perhaps taxed her leg/hip a bit, it didn't show up as pain until the barometer dropped. I know some folks disagree with that notion, but I think it is a factor for some.
Your job sounds a lot like my teaching job was---you are probably on your feet most of the time, and so busy you may not even be thinking about any aches and pains you have....until you get home and sit for awhile. And then you become aware that something hurts!
I agree it is worrisome when a new pain pops up, or you feel like you are having a setback. I feel like I am having a little more pain now as well, following a very smooth early recovery. I intentionally did not push myself and eased into things. Now that spring is approaching and I am increasing my yard work, outdoor walking, etc. I think I am experiencing some of the adjustment that is normal for anyone. It certainly is something I've had other springs---my "gardener's bottom" pain.
But for some reason this year, it makes me nervous because I am associating it with my new hip. Just something I need to get past mentally I think. I hope you get back on the "smooth recovery" plan! I know the feeling---afraid to feel too good about doing well, for fear it may fall apart!