I have a deep throbbing pain in my calf muscle while going up and down the stairs and during football practice but no other time?

Sounds muscular: The fact it involves only certain weight bearing activities suggests that it is muscular issue, most likely pulled or strained muscle. If it was stress fracture, it would hurt most likely with all weight bearing activities & would present like a shin splint in the front of leg, not where the bulk of the muscles are found like the calf. See your doctor for evaluation & treatment if painful enough.