before now, how long has it been since you last did any type of pysical activity? are you over weight currently? do you have any health issues?
may i ask do you smoke if so thats the cause of your problem i have the same symtpoms , id walk for a bit then my calf muscles would hurt to a point id have to stop for a while until i can walk again.....i learned that this is caused by your leg arteries supplying blood to your leg muscles are being narrowed and less blood is reaching your calf muscles causing the heavy pain....if you do not smoke then you should refer to a vascular surgeon if possible....