Hold on hold on......it might be a very simple thing: your body recovering from running a marathon! All you might need is a little rest. You have just done 262 miles. No easy feat. At a really good time. Your body might just be crying out for some R&R.
i'd have a couple of weeks off. Maybe do swimming or aqua jogging if you still want to exercise. And if you are then still out of breath, see the GP.
Sounds as though you are doing everything. It sucks not running. I would try aqua jogging. It's boring as hell, but I really do think it helps. i wouldn't run until pain free and then ease back into it.