^^ the calf thing i used to get when i started back running.. Theyd get a tight and burning feeling?? Sucked bigtime and i felt i could run longer but the pain was too much.. If thats the same itll go away probably after 6-8 weeks.. I dont think its a circulatory issue.. More an "out of shape" one
In the meantime id suggest u try to incorporate intervals.. Which it sounds as though ur doing a form of them already.. If u can find somewhere (like a park or field) and pick 2 points a distance u feel like u can sprint without stopping.. And sprint from one end to the other and walk back and repeat.. Each sprint and walk back being 1 set.. Try to do 10 sets.. As u progress increase the amt of sets.. Very good cardio! Ud only need to spend about 30 mins doin that.. Once u get in better shape finish the round off with a 10-15 min jog...