I will try my best to answer your query.
The medical world does not have any drugs that are indicated for breast growth or are prescribed for that purpose, except synthetic estrogen
which can be given in cases of gender reassignment to cause a biological male to grow breasts. This would not be expected to work in biological females as their bodies are already under the influence of estrogen.
If your breast size is causing you significant psychological problems, discuss this with your GP who may know a sympathetic cosmetic surgeon able to provide you with implants.
Surgery is the only guaranteed way of increasing your breast size.
To reduce abdomen regular diet and exercise will be helpful.
Hope my answer will be helpful for you.