I have pain in the same area. I did a Google search for "pain in the balls of my feet" and came across a condition called Morton's Neuroma. You should check it out. It sounds exactly like the pain I'm having.
This may or may not be applicable to your situation. I had PF going on for some time ( pain in the heel and arch). To deal with that while being on my feet on concrete floors, I put more of my weight on the ball of my foot. Basically I limped for a month.
Then one day as I got up to walk through the kitchen a bone popped in my foot. Right in the center of the ball of my foot. Felt like the bone was going to come poking out the bottom. It had been hurting, swelling for days before this. After 2 weeks, visits to a family practice dr., my chiropractor, and finally the podiatrist we got an x-ray that confirmed a stress fracture.
I don't think that is where most people get stress fractures. Forgive me if this did not apply to you....