How can I control pain from plantar fasciiatis (flat feet)?

I have had severe pain from this off and on for years, but it is really affecting my ability to exercise regularly, and I do not want to give that up. I have tried stretching the area, like my doctor advised years ago, but this no longer seems to do much good in relieving the problem. Recent attempts at learning yoga have been disastrous regarding my problem to the extent that I can barely hobble through my home following a workout. Also, when I try to use my mini stepper, the same excruciating pain develops. I had heard of a surgical procedure to aleviate the problem, but am worried that it will take away some mobility.