Loosing weight is indeed very difficult but a disciplined approach can definitely make you attain your goal.
First of all you should get your thyroid function checked to look for hypothyroidism
because hypothyoroidism is a very commonly occurring problem which results in weight gain.
Now I would explain you the mathematics of weight loss
To lose one pound by exercising, you need to burn approximately 3,500 calories. (2.2 pound is one kg).
This can be done by exercising and cutting calories.
Walking or jogging uses roughly 100 calories per mile.
One would lose a pound for every 35 miles of walk (provided food intake and other activities are constant.)
Walking briskly (4 miles per hour) for 30 minutes on five days a week will be equal to walking 10 miles a week. So it would take 3 ½ weeks to lose one pound (provided the number of calories stays the same.
Cutting back by 250 calories a day (½ cup of ice cream or two sugar-sweetened sodas) will lead to a loss of a pound in two weeks.
By eating 250 fewer calories and walking for 30 minutes a day, it would take a week to lose one pound.
So be realistic and aim for loosing only one pound a week and this way your weight loss would be achievable and permanent.