Cut it down to one longer run. try 3 miles and build up till you can do 4 or 5 without killing youself....Get some other form of aerobics or something in place of the second run....Though running is good cardio it's not the only kind you need...Just because you can run alot doesn't mean all muscle groups are getting benefit....add others to it....I suggest a Pilates workout at a quicker pace or maybe ti-bo some people think that sounds funny but give it a try....I know guys who can run 10miles but cant finish an advanced ti-bo workout