Definitely check out pulses and mobility of nerves, agree that generally if bilateral problem it may well be central in origin.

Pain on the inside of the calf can often be caused by medial periostitis, irritation where the facia attaches to the shin bones.

Generally where the symptoms are bilateral I have found that one leg is significantly worse than the other if it is not circulatory or neurologically related.

Definitely try and get to the bottom of your symptoms as I have seen a lot of cases of stress fractures in this area, where patients have ignored symptoms. Bone scanning has confirmed the diagnosis, however I don't feel that this is generally necessary, as it does not tend to change the treatment.

Biomechanics may be a large factor...
overpronation, tight calf complex, poor popliteus control (lack of locking / unlocking mechanism at knee may be affected), glut. med. control is often poor

Overtraining is often a big factor, you may need to vary the type of training you are doing, reduce the amount of impact activities etc... You can work on endurance and fitness with various low / lower impact work

Recover is important, allowing time for muscle damage (following a session) to recover, having the correct nutrition to optimise healing etc..

If it is musculoskeletal in origin then rest, appropriate strengthening and stretching, improvement of biomechanical issues and a graded return to activity (without aggrevating symptoms) is what is required.

Good luck.