My calves have been feeling really heavy, cramping up and hurting when i do activities that i always/regularly do ie. running. why? how do i fix this?

Bilateral calf pain: Muscle/Achilles if not warming up properly/ stretching, worn/ improperly footwear, uncorrected flat feet, low -potassium, magnesium, calcium or sodium. When exercising drink fluids-a mix of water and electrolytes like Gatorade/juices/ coconut water (pure water dilutes sodium causing collapse). Make sure you have adequate Vit D. Rarely clots- usually unilateral. Follow with doctor/urgent care.

Warm up and hydrate: Muscles often cramp when subjected to sudden intense activity and are cold. Cramping also occurs with dehydration. To prevent cramping of muscles, make sure you warm them up ( do your activity at low intensity for the first 10 minutes) and keep hydrated ( drink water).

See doctor: It is possible that you have a myositis which would require blood work to diagnose. A blood clot is another possiblity which would require test, but the doctors physical examination would also suggest this. If it were the usual training discomfort I doubt that you would be asking us about it as you would already know what to do. There are medications for the cramping and hurting