Sounds to me that you may be suffering from acute exertional anterior and/or lateral compartment syndrome. This is where your fascia tissue does not accommodate the expansion requirements of your muscle under prolonged exertion (typically running and fast walking). As a consequence your may be feeling a distinct pressure build up in the anterior and lateral compartment of your calf muscle.
I myself have bilateral anterior and lateral compartment syndrome, so I know how prohibiting this condition can be.
My advice would be to get some proper diagnostics done by an appropriate musculoskeletal physician or sports medicine specialist.
If your physician concurs with my hypothesis upon your initial consultation, he or she will make appropriate arrangements for you to undertake ‘pressure studies’.
This entails injecting a local aesthetic into the area of complaint. From this you will be in all probability put on a treadmill and be made to run as a means of bring forth the symptomatology that you usually experience. From this, the physician will plunge a sizable needle into the area that has been numbed (don’t worry you wont feel a thing). Attached to this needle is syringe plunger like object.
This will be used to measure the amount of pressure in the area of concern. In normal post exertional circumstances (as told by my physician), the pressure reading will be around 20 (mmHg). However, in my circumstances where compartment syndrome is apparent, a pressure reading will be double that. In my circumstances, I had a reading of 53 (mmHg) in my anterior compartment. This is a clear-cut case of compartment syndrome.
You have indicated that you have exhausted all conservative remedies (eg massage, ice etc). The advice I have received from the physicians I have talked to (I work in the healthcare industry so I know some of best guys in the business) and my review of the literature on this condition (pubmed is great for this), the only viable remedy is surgical. The procedure is called fasciotomy/fasciectomy. This is where they surgically cut away at the fascia tissue as a means of relieving the pressure.
As a final note, I would advise that you should actively seek out the most reputable sports/musculoskeletal physician in your city. Most doctors in general practice do not know much about this condition (or musculoskeletal complaints in general) and you don’t want to be f&*king around with referral after referral and futile diagnostics.
I hope this information is of assistance and good luck in quest for a diagnosis and remedy.
p.s This is general information and not meant to replace the advice that one would receive from a qualified physician (I know too many lawyers!lol).