That could be due to limitations in the capacity of your cardio system, your leg muscles aren't strong enough / does not have the endurace capacity, or both.

The quickest and most effective way of raising your cardio capacity is doing intervals: Doing close-to-max intensity for a short period, then a period of low intensity (not rest), then repeat. http://en.wikipedia.org/wiki/Interval_training. It does not have to be running - you can alternate with cycling or whatever, cardio training is cardio training.


Training your leg muscles to take the abuse of jogging is something that takes time. As discussed earlier, be careful and listen to your body signals. You want to stress the muscles, joints and tendons enough to grow them stronger, then let them have the time to recover. Too much stress or too little rest and you have an injury that potentially takes a long time to recoup from.


You could also target specifically exercises for the spring in your step (jumping rope, jumping up and down from low benches and so on). Stronger muscles equals more spring equals better running. That may or may not be one limiting factor for you, hard to tell from where I am sitting...