If you are female, you are 5 times more likely to clench, which can create stiffness in your neck, back and shoulders.
If you have pain only when you exercise, it is very likely that your feet and eyes, in their roles as sensors, are dysfunctional.
If you have pain at rest, the likelihood is that, on top of your feet and eyes being dysfunctional in their role to stabilize your posture, your bite and/or your skin and abnormalities to these organs is a component of your symptoms. An issue with the bite can be a click when you open the mouth and an example of an issue with your skin can be a surgical scar.
If your pain in worse in the morning, before you get out of bed, the symptoms you have at this point are likely to be caused by clenching at night. If the pain is in the afternoon/evening, the improper tracking of your eyes is likely the culprit. If your symptoms do not change much from morning to night, the asymmetry of your base of support provided by your feet is likely the main issue.
If your pain is mostly in your upper body, the main organs that are causative are your eyes and your bite. If your pain is in the lower half of the body, the foot is more likely to be the cause.
If your pain is located more so on one side of the body, the eye or the bite are more likely to be the cause. If it is on both sides, the foot is probably more so the cause.
If you sometimes feel like you are losing balance, you could be dealing with an inner ear dysfunction. In this case, an ENT could evaluate you. If the results of this type of investigation are negative, a sensory deficit coming mainly from your feet and eyes could be at the source of this sensation of instability.