ok that helps, thanks, milers
pronation is probably the key to unraveling this problem.
do you get any metatarsal pain as well? any IT pain on that side? or have a narrow heel?
then, w/ rubber tubing, strengthen the anterior tibialis and the peroneous longus, a lateral stabilizer. technically you can do both strengthen those muscles and stretch your calves this way because the calf will relax when the antagonist muscle group is flexing.
from your description cant rule out limb length issues (sore achilles would be long side). could also be dueovercorrection if you had too much of an orthotic.
my guess thoough is you pronate, guard the leg, and jam the spot on the achilles with a sharp torsion strain.
and cant rule out bursitis, but the same nutritional ideas will serve.
anyway achilles are made out of collagen primarily.
collagen is a type of protien matrix that kinda winds like a rope, so any torque or twisting or eccentric force could cause damage.
so will elevated blood sugar levels, so cut back on processed sweets and try smaller meals. grazing not gorging. antioxidants are natural anti inflammatories, as is the mineral magnesium.
since youre a kid my hunch is a heel cup might help solve the problem. first it will stabilize the heel a bit , protect the lower achilles from irritation. just avoid the extra soft visco-elastic ones which in your case might add instability. you want a fairly firm heel cup. the slight lift on the cup will also take some pressure off the achilles.
here's a link on collagen. collagen production is stimulated by vitamin C. as I recall, proline is one of the more important amino acids for repairing tendons.
http://au.health.yahoo.com/041101/25/1uvl.html