An H cup with a petite frame suggests a very dense full breast or a longer more sagging breast. Both breasts can be reduced to a smaller size. There are different techniques to reduce and reshape the breasts depending on your anatomy and the desire to minimize scars. I commonly see young women who have petite frames with very large breasts who want to be "as small as possible". I empathize, for if I had the same frustration, I would ask for the same solution. A B cup after reduction or even a small C cup is not the same as the woman who is frustrated wearing a B bra who wants augmentation. A B can be a very pretty size and needs to fit your body.
The only way to know is to have computer imaging. Putting different size implants into you bra may help but an in person consultation especially if the doctor has Crisalix 3D imaging you can get a good idea as to how you will look.