Calf pain while running?

I'm in my 6th week of training to run for a 1/2 marathon. I started off slow and I am only up to 6 miles nonstop running. The problem is that a 1/2 mile into my run my calves lock up, then around 1 mile I start getting shin splints and then eventually my feet go numb (my calves feel hard as rocks when I stop). I am doing everything I am supposed to be doing, I am really hydrated, stretching in the morning, before my run and after. I am also eating an extremely healthy diet. I went and had my run evaluated and I have an almost perfect gate, they also recommended shoes for the way that I run. I am at a total loss what to do for my calves! This is starting to hold me back, because it's almost impossible to continue running. I used to wear high heels almost every day for years, do you think it's possible that I permanently damaged my calf muscle? If so, how do I fix it?