Lower leg pain

Hi guys
I am a free time runner where I normally run 3 times a week some times more and some times less, normally I run for 15-20minute on flat surface after walking for at least 30 min and doing some stretching, but a while ago I started to walk into a near by hill for around 50 min and then run down the hill and on flat surface for around 30 min but when I went back to running only on flat surface it takes me 7 to 8 min until I feel real pain in my lower leg between the leg and the knee mostly in the from but also in the rear and then I cant continue running I feel the muscles over by bones contracting and never relaxing, thought it may be because of the shoe (I run using a basketball shoe), or maybe I was pushing myself to much but rest doesn’t seem to help what is your advice… by the way the pain goes after I stop and stretc.