What kind of exercise are you doing? Reason I ask is because as one ages, one loses muscle mass unless one is doing a solid weight-training routine. This one reason why, say, someone who only runs or does aerobics faithfully for years will still gain a bunch of weight and body fat, because they haven't addressed the muscle issue. Cardio is great for your heart, endurance, but does nothing to maintain or increase muscle mass in the body. The cellulite issue is also because of the fact as one ages, the skin is less elastic and thins out with age, thus making underlying fat more visible. I'd be willing to bet if you got yourself to the gym, and also changed your diet to much less sugar and refined starchy carbohydrates, you will be able to shift your body composition to a firmer one. Granted, this takes longer when you're older, but it is definitely possible. Make most of your carbs vegetable and fruit ones, and add a bit of lean protein to your meals. If you do have starchy carbs, make them unrefined, like brown rice, oatmeal, squashes and tubers(like yams and carrots). Reason for avoiding refined, and even TOO many unrefined starchy carbs at this time is because our digestion changes such that these types of carbs tend to go to increased body fat instead of being used for energy the way they are in younger women and most men. Avoid alcohol too. I know there are people out there who say a glass of wine per day is fine, but for many of us, especially those at high risk of breast cancer, it is a total no-no. Also, it really messes with hormonal balance at this time of life as well.
Hope this helps!