I do have an x-ray for tomorrow just to rule out a stress fracture as a cause (even though if I had one, I'd probably know more about it) at least that will rule out one possible cause. There may be a couple of other things going on, including some ligament irritation on the outside of my foot where the initial pain after the half marathon was the worst, and this may just require a little more time to come right.
So, if I can get out for a 20-30 minute run twice a week and swim a couple of other days a week, I will be a happy girl. Hopefully it'll be light enough to encourage healing on it's own, but it'll be enough for me not to feel like I'm missing out on running so much. It's felt like a VERY long two weeks!