Judging strictly by my own bout with plantar faciitis, what you describe doesn't sound like it, but I'm no doctor nor do I play one on TV. PF is, in my case, indicated by a more localized and sharp pain in the bottom of the heel area.
I developed PF due to running even though I had prescription orthotics and stayed off concrete. I believe it came about due to my tendency to be a midfoot striker combined with doing too much speedwork and hills without easy days.
Once it developed, I got immediate relief only through cortisone shots, but I and any physician would recommend doing this sparingly as it's my understanding that too many injections into the same general area can lead to a weakening of tendons and ligaments in the area, predisposing them to ruptures/severing.
In severe cases, surgical severing of the plantar fascia may be called for. How and why this is done, I don't know. All I know is that one girl in our running club got it done and was still able to qualify next year for the Olympic trials in the marathon.
PF plagued me off and on for probably close to six years, though it fortunately became less of a pain (literally) in the later stages. This coincided with more attention and time paid to stretching. I also bought what's known as a Step Stretch. It's a crescent-shaped thing that you step on and rock back and forth slowly on. Stretches your calf and, to a lesser degree, the foot.
In addition, there's a device available that basically locks your foot and ankle into a 90-degree position, and you wear that at night. I've been told this works well. You can check the aforementioned devices at [url]www.roadrunnersports.com[/url]. Good luck; it sucks to be hurt. [:(]