I have never helped anybody with your condition, nor have I treated it in my own body so take this with a grain of salt.
Get a strap, preferably a thin one. Come to your knees and strap your ankles together. Put the locking mechanism between your ankles and then sit in virasana (knees together) on the tops of your feet. You will notice that the strap keeps your ankles together where they would naturally want to fall apart. The part that I think would be good for you comes a few minutes after you take time on the tops of your feet. Tuck your toes and sit back to virasana. Be sure that you are not learning forward as this is a common response. I recommend the first time you do this that you take a blanket and put it between the back of your thighs and calves.
You may also roll up a blanket slightly and put it somewhere but I don't quite remember if it was under the ankles or under the butt. I hesitate because I don't want to be one of those teachers that has people but blankets under there knees rather than under their calves in dandasana.
Note that this pose/counter pose sequence can hurt like a mo fo. The first time I did it was the most willpower I have ever had to exert in a yoga class. Afterwords my feet felt fantastic!
To treat just above this area you can give this a try and may wish to do this first.
Come to a wall.
Put your feet together and slide one foot back. Keep the alignment that you had with big toes touching and keep both feet facing forwards. You see runners do this stretch a lot with their back leg turned; this is incorrect. Starting with the calf stretch, bend your front leg and straighten your back leg, internally rotating your thigh. Keep the ankle grounded. For the achilles stretch bend the back leg. You will have to bend a little less in the front leg to do this. Keep the ankle grounded. Also, be sure that your are not collapsing your chest and resting your upper body on the wall for both of these.
You may also consider learning about the triangles in your feet. I would think it is possible that you are putting too much weight on the insides of your feet. You may also use the visualization of grounding down through four corners of your feet, but I prefer the triangle visual.
Enjoy your new behavior modification! Sometimes we need to slow down and look to postures that we otherwise shrug off as simple, or easy.