First the back. And now the top of my foot hurts all the time. What could be wrong?

Neuritis. You may have an injury to the back that is pressing on a nerve to the lower extremity creating a neuritis. You should probable see a back specialist.
More info needed. To receive an answer that will be more helpful, you need to give more information...Your health status, any problems such as gout, diabetes or blood pressure concerns. You should state how long it has been a problem and what you do to make it feel better. Also tells us what it looks like. Is it discolored, swollen or point tender. The more you tell the better the answer.