You don't mention your age so I can't tell if you're still growing or not but I can offer the following:
To increase the size of your butt without just adding fat try exercises such as squats, lunges and deadlifts. Be careful tho, because if using weights strict form is important for safety. These exercises will increase the muscle mass of your thighs and butt. Don't worry, you won't get muscle bound overnight - you'll have to work hard for the muscle you gain!
I know increasing your bodyfat will probably increase your breast size but this is probably neither ideal nor healthy. The only way I have heard of naturally increasing breast size is using visualization and mental imagery/mind power techniques - I read about it once but this may seem a bit "out there" for you.
THE ONLY WAY TO ACHIEVE BIGGER BREASTS WITHOUT SURGERY IS TO GAIN WEIGHT!
The best way to make your breast area bigger and firmer is to exercise the muscles in this area. Some good exercises for this area are: - push ups - benching (lifting a barbell while lying on your back) - push ups and dumbell flies (lie on the ground or a Weightlifting bench with your arms sideways. Have a dumbell in each hand. Lift those dumbells until they are above your chest slowly, then move them back.).
In exercise the most common way is doing 3 sets of 10 repetitions of an exercise. Rest after each set.
you should relax, im a guy and i dont follow that streotype of liking big breasts, i prefer smaller flatter women.
If you are developing, then just let nature take it's course and just don't worry about it.
If you are an adult, than the only solutions I can offer you are to accept your chest size, or go under pricey cosmetic surgery.