Why does the outside of my right foot hurts when I work out?

I have lost 25 lbs recently through a well balanced diet and exercise. Recently the outside of my right foot has started hurting and feeling very unbalanced but only when wearing my sneakers. It hasn't ever happened before. My sneakers show no wear on the bottom. I tried insoles to no avail. Any ideas? I called a podiatrist but cannot be seen until august. So any advice? Suggestions?