morning foot pain

Every morning I wake up with foot pain.
It hurts everywhere when I walk for a minute or two.
Then it is fine for most of the day.
This has been happening for months.
I am a lifeguard, and I have worn Birkenstocks the last few years at work. This year I had a pair of Reef Thongs.
Could this have made a difference?
I worked this summer 5 days a week, walking on a concrete surface.
Pool season is over now but I still have the foot pain.
Help!!!!!