My breast started growing at the age of 12, and nw it is showing sign of improvement just a little
Breast growth continues in almost all women until at least age 16, often continuing for several years beyond. The growth pattern varies, and is not always linear--it can happen in spurts. The growth pattern in female relatives may be predictive. Good reassurance can better come from your pediatrician/ family practictioner. All the best.
You normally will see breasts develop at the time of puberty, but it goes on through the teenage years until the early 20's. Some develop early, some develop late. There is no way to predict things. I would not recommend considering surgery for underdeveloped breasts till 18 years old.