Hi- I dont do cardio, so cant really give advice
Maybe try varying your diet, for example (I do low carbs for 7days and a high carb meal) so maybe I'd do low carbs (10g or less a day),for a fewdays, but then try very low calories one day, or high on a busy day....to stop your metabolism getting stagnant

I truly believe nutrition is 80%....so look into that more than the exercise and check out Vince Gironda