Calf pain (unknown reason may be overuse) for 10months. no visible signs from outside. scan confirmed no blood clots. walking makes worse and resting,massaging,and stretching make feel better almost immediately. but the tight pain keep coming back?

You have ruled out venous blood clots but have you been checked for arterial blockages? If both calves are bothering you blockages in the abdominal aortic or iliac arteries can be a cause of your symptoms ( claudication). If no arterial pathology, a primary muscle disorder is a possibility. Your MD or a vascular surgeon could look further into your case, order any appropriate testin & advise you

Yes it can be an overuse injury. You say you do all the correct things but when you stretch it may be incorrect in your methods. You need a structured program. Physical therapist , podiatrist, sports medicine MD or DO. are your best sources.