Hello Saunskruti, when we talk about exercise 5 thinks are to be taken into consideration mode,intensity,duration,frequency and rate of progression. If you are doing aerobic exercise for 6-8 weeks your body gets adapted and response to particular exercise fades. You need to modify your exercise plan,it can be by changing mode i.e cycling.running,hiking,step aerobics etc. You can also increase you exercise intensity,duration or frequency,depending on what suits you best.
Also remember initially the rate at which you loose weight will not be later.Be consistent with your exercise.You will achieve your goal.
take care.