kitcat

i really enjoy working out, even though sometimes i find myself lazy. but it seems that after my runs, or even at the gym on the elliptical machine i am just plain exhausted to the point where all i can do i lye in bed. im wondering if maybe im burning myself out too much, and what to do about it? (i run 8k lightly for an hour) apparently you need rest days, but if i want to loose weight i dont understand how to work it all in? and how many rest days do you need?